I know there only a few, but I see teams with constant S16 or better stretches for multiple seasons.  With me I've dealt with sever IQ problems limited my teams effectiveness when my classes are short on IQ, however it seems a lot of these schools don't have too much more balanced classes for me.

For example when my Cal Tech team (I sort of run a 4-4-2-2 class) was heavy in upperclassmen I managed a S16 and E8 When I went to 4-2-2-4 I dropped to a PI F4 and then a PI 3rd round this season(with 3 upperclassmen).  While having the 9th best team ath and def ratings, just not enough IQ.

Is a 4-4-2-2 structure still not balanced enough and that low IQ killing me.  Its really frustrating during the down years, because I have some amazing freshmen/soph and it seems like it just doesn't matter and I lose to heavy loaded upperclassmen teams with much weaker ratings....

Sorry just a little venting

My Maryville team currently has a 4-4-2-2 structure (although that is prone to change, because I redshirt a guy most years but not every year) and is definitely on a pretty good run right now. We have won titles with only four upperclassmen. 

That said, it's hard for me to really tell you the secret, because I don't know it. I've definitely taken my fair share of low WE guys, so it's not just like my guys develop super quickly. And it's not just clever coaching, because I haven't been able to duplicate it with any other team. I think it's just a combination of numerous factors including both skill and luck--what recruits you're able to get, what teams you end up facing in the NT, etc. 

With a 4-4-2-2, I definitely think that you should be able to make the NT every season and possibly make the 2nd round every season if you're really good. As for streaks of Sweet Sixteens or Elite Eights, I know coaches who have them, and I have had them myself (in addition to Maryville, I had five straight Sweet Sixteens with Greensboro, but that's over--my Greensboro team isn't even PIT-worthy this season), but I think they depend in large part on just having players who can contribute unusually well as freshmen and sophomores. I have not been able to make those runs consistently in different worlds. There are definitely coaches better than me, and maybe some who can do this consistently in multiple worlds (jsajsa and tianyi come to mind), but I honestly don't know how it's done. 

Taking a look at your Caltech team in particular, the biggest problem I can see is positional imbalance. You have four freshmen. Every single one of them is a guard. Not only do you have zero upperclassmen at either PG or SG, you only have one sophomore. If you had three sophomores and two freshmen at guard and two upperclassmen, one sophomore, and two freshmen in the post--rather than your current setup of one sophomore and four freshmen at guard and two upperclassmen and three sophomores in the post--I suspect things would be going much better. 

2nd thing I notice: you only have one rebounder in the post. You should have more. 

3rd thing I notice: you have eight games on your schedule against teams with RPIs between 50 and 175. You went 4-4 in those games, so you weren't exactly setting the world on fire, but you did pick up two more PIT wins, so obviously you can compete against middling teams. But you don't play enough middling teams. Those RPI 200+ games are killer. You can't avoid the ones in your conference, but don't have three on your non-con schedule. Also, if your team is going to be young and borderline NT, don't put Final Four teams on your non-con schedule (unless it's a rivalry that you play every year or something). 

Don't get so caught up in class structure. If you want to be good every season you should definitely try to keep it so that you never have more than 9 in back to back classes, but you should be more worried about recruiting players that fit your team needs for now and the future over keeping a defined structure in place. Everything being equal in terms of team needs, would you pass on the redshirt juco option when a star falls into your lap because you need a freshmen to fill a class balance? Consistency is about successfully projecting you team needs over multiple seasons and finding the players that fit. A consistent class structure is not high on the list of priorities.

This will sound so simple that it will seem stupid, but the easiest way to remain competitive like you're talking about is to consistently recruit top notch players.  That, combined with even a semi-balanced class structure, will keep you competitive season after season after season.

Tarvolon also brings up a good point that is often overlooked by newer coaches.  Your non-con schedule can be extremely important in determining how your season will play out.  If you've got a young team, play an easier non-con schedule, it's that simple.  A more experienced team can probably handle a tougher non-con schedule.  It's really as simple as that.  Don't over think this game, it's not rocket science.

I think a lot of newer coaches also accept all comers in non-conf, and that's really foolish. if your team has literally 0% chance to win a game, don't accept it. going 1-9 or 0-10 against a brutal non conf slate will not get you anywhere except a longer wait between seasons. it's also difficult to build your prestige with bad w-l records which also contributes to consistency (or lack thereof).

jsa and tarvolon nailed it. class structure isn't that particular, 4-4-2-2 is a very balanced structure as is. its really about fitting the team needs. having all 4 freshman guards is absolutely brutal, its VASTLY more important to maintain balance by position/role than to maintain balance in class structure. if you had your 2-2-4-4 year, with 2 guards in the upperclassmen classes, along with 2 more players from the 3-5, and they were all quality players, you really have plenty of experience - the 4 sophs will fill the other starting spot and you still have 3 key backups. more experienced teams, like a 5-5-2-0 structure, are only marginally better than you from the IQ.

note that its not just position, but role. one of the most vital roles on most team setups, is a lead per scorer. if you don't have a high end perimeter scorer on a team, that is going to crush you (unless you are one of the small % of coaches who build fta based offenses well). if that guy is a senior or a junior, it doesn't really matter from the iq, but the dropoff from having a great dude score 18ppg to having to pick up those points with scrubs is massive. i mean thats a whole round of advancement in the NT difference potentially right there on one guy. meanwhile taking a junior to a senior IQ is generally under 1ppg difference. 

Good stuff. It took me about a year to start really looking at non conference games closely. I think Gillespie or someone else gave me that advice and it helped s lot. I also started being more patient in scheduling. Now I usually wait to schedule for the Next Season to see how good a team is likely to be so I can avoid those killer sub 300 rpi games on my non con schedule.

Sign somewhere between 2-4 players per season - the exact class balance doesn't matter. Try to fill all your available slots every year with good players. Have a very strong grasp on how your players will progress, what their roles will be, and recruit guys who complement one another. You aren't recruiting to fill the roles that just opened up due to graduation - you're recruiting to fill the roles that will be needed in 2-3 years. You should be starting almost exclusively seniors and juniors every year.

Those are the strategies I used and I just finished a 20 year stretch where I finished in the RPI top ten 19 times. I very rarely had more than 7 or less than 5 upperclassmen. I was fortunate to have a nice recruiting base, but those strategies will serve you well in any situation.

I feel your pain regarding facing superclass teams in the NT. Early in that run, when I was fairly new to HD, I lost in the Elite 8 or Sweet 16 several consecutive years to superclass teams that went on to win the title. The next year they'd fall off the map, I'd go back to the Elite 8 and lose to a different superclass team. Rinse and repeat. After the third or fourth time I thought that must be the only way to win, and planned on transitioning to a superclass model after the next season. Well that next season I won my first title, so I stuck with the balanced set-up and never looked back.