I guess it really depends on your division as well. If after 3-4 years you are winning the conference every year with no real competition, you should be starting your Fr/So during the regular season every time, just to build their WEs early on, then just change to your top guys in the conference championship and playoffs. You'll still win all your games just by being better than the SIMs, and it'll make your recruits that much better. Check out St. Olaf, who does this in every world, and as a result is always a top 4 team.
For the record, starting all Fr in the first year of a rebuild, the team went 7-6, then 10-3, then 12-2, and that was in a conference with 4-5 users so more than normal. You'll get the high vision pretty quickly regardless just by having non-SIM players and playing SIMs mostly. As I mentioned, I didn't keep starting new Fr. every year, but those first recruits started all the way through Sr. year, and by the end they were all top guys despite originally being very average (all had high potential of course).