Generally speaking, you want to get max value out of pre flop monsters like AA and KK. That said, how can you expect to get max value out of these hands by limping into an unraised pot?
Assume that you are first to act, you limp and get 3 limpers behind you. Your AA or KK just lost significant value on the flop because you allowed 3 weaker hands to limp into the pot along with you, making your vulnerable to drawing hands, lower sets, 2 pair, etc.
I can only think of 1 circumstance where it would be a somewhat acceptable play to slow play PF monster hands. If you are at a LAG table and UTG I could see checking your PF monster with the intention of making a larger than pot size re-raise to any raise in the pot PF. The idea here is to sweeten the pot by getting liberal calls to the initial raise, and then take away pot odds
for loose callers and try to isolate the initial raise in the hand. You don't want to take AA into a multi way pot post flop, because there are just too many things that can go wrong.