Rock n play at night

My ebf 6 week old sleeps 5-8 hour stretches at night, in the rock n play. I know eventually he will have to go to his crib, and I'm worried he will stop sleeping so long!! When would you start to try? Every night I tell myself to put him in the bassinet (at least it is flat), but I'm just too nervous to give up my sleep! Ha! When would you try? Anyone else doing this?