No break in period needed for these! Love the dad sneaker trend and these are it!! So comfortable immediately upon trying them on. Walked about a mile and half the first day of wearing them and they’re so comfortable—which I was surprised since I haven’t had the best lucky with Nike in the past few years. Very cushion-y in the heels. I think I could’ve gone down a half size, I normally and a 6-6.5 and got a 6.5 in these. I think I would have been ok with a 6 too. But I’ll keep the 6.5 since they were pretty comfortable already. Highly recommend!