I think back to what (I think) Mike said in an earlier thread: if you can compete for the playoffs this year, then why keep guys that can help you win at AAA for the first 20 games (10 of which are against division rivals), just to get one more year out of them 10 years down the road?
Maybe you don't plan to contend this year, but if you do, I'd bring them up. In the case of position players, I'd say only surefire future Hall of Famers are worth getting the extra season down the road. Especially since you're going to have another 10 seasons of draft picks to develop while you wait for these 8 guys to hit free agency.