Breastfeeding Question

So before I conceived I would drink a cup of coffee every day, even liked to enjoy a red bull maybe once a week. I have completely cut out caffeine since becoming pregnant. It is SO hard but I'm doing it for my baby. Now when they're born & I breastfeed do you guys think it's alright for me to go back go a cup of coffee a day? And how long should I breastfeed?