I usually think of it this way: The first season of the switch you should only play your old offense, unless you know you aren't making the postseason anyway. In that case, just start playing the new offense because it won't matter. By switching your offense, you're essentially making all of your players, at least offensively, into freshman because they're starting at scratch with IQ. So if you switch to playing your new offense at conference play (a dumb idea, either switch it now and tank the season or continue playing the old offense while your players learn the new,) your seniors will now have the offensive IQs of a true freshman at that point of the season. Even though their skills are likely much better than an incoming freshman's, the offense will still be hurt quite a bit.
Also, next season, all of your players, with the exception of the incoming freshmen, will have offensive IQs equivalent to sophmores. That's how I usually think of it and it helps prepare me for how bad my team is likely going to be.
On a side note: why are you changing again? If your thinking about flex, it doesn't seem worth it to me. Triangle to flex won't make much of a difference other than to ruin a couple seasons for you. Triangle to motion? You want to spread the ball around more? I don't know, I'd personally stick with triangle where I can have 2-3 go to scorers and still have an effective offense instead of needing scoring from all my starters.