i haven't used diff clothes for daytime & nights really - well, apart from putting DS in a clean suit after his bath. DS has mostly worn some sort of all in one suit so far (no legs with pants & the full suits) and has only recently worn tops & pants. i think we'll introduce the idea of pj's in a few months but no need yet (i don't think!)

if you're worried about colder nights, you could always get a couple of the bodysuits or even wait until he's born & then buy them if you do need them