I wear a bra 24/7 now and did during my prg with DD as well from about 15 weeks. I read that having support even when you're sleeping can help to prevent stretch marks in bigger breasted woman (that's me!!) I didn't get a single stretch mark so I thought I'd stick with it this time too! And they are so huge I just find the support more comfortable.

I b/fed DD for 16 months and I wore a bra pretty much 24/7 then. But if I were smaller breasted it would probably be a different story.