What Woodbridge is referring to is pretty common. What I have found less common is people buying players 32+. In some cases when you buy a 32+ player, you will get him at a deep discount in relation to the same skilled player at 28. A lot of times I see teams geared towards this strategy (like mine). So its either drop them at 32+ or buy them at 32+.
On my team I carry 6 players at age 33+ with having a career extension trainer. Although skill drops hurt, to me they are few and far between. I believe the average seems to be around 3-4 skill drops a season. Which means if you find a well rounded player, you might be able to have him as a starter a season or two, and then convert him to a backup as his skills fall.
Now most of the time I currently do one pos training. Sometimes I will carry up to 6 trainees. But I only have 3 main trainees. The other three are train n sell types that I pickup for when I need to a two pos training.