I wear a bra pretty much 24/7 now! And I will wear it right up until teh new bub stops b/f. That's what I did with DD.

At night I tend to wear a lighter support sports crop thing (which will change to a light suppport feeding bra). During the day I need a good supporting bra. I am about a DD-E at the moment.

My advice - if you want to try to eliminate the possibility of strech marks, wear a bra as often as possible.