I've been in normal bras for a long time now, and I'm still breastfeeding LOL. Went shopping one day coz I was sick of the unflattering maternity bras.

I say just give it a go. If you're worried about mastitis (I'm assuming this is why?) I can usually tell little niggles before anything happens so then swap back to a softer bra for a few days. I guess if you're prone to mastitis then stay away until you feel like the lactation has stopped.