My baby daughter is 4 months old and is getting harder too burp. It's been a long time since I've done this (my oldest daughter is 12) and I cant remember at what point I stopped burping.
Some babies don't take in a lot of air when eating and just aren't big burpers. My dd has never needed much burping and at 6 mo. I can't even tell you the last time I tried burping her.
My ped said if after one min. they do not burp, then they don't have too. My ds who is 2 months burps very well and sometimes he just does it on his own.
my health visitor said you only need to burp at most once during bottle and at the end. she says rub their back for 5 mins if nothing happens you will find when they are next picked up and wind will escsape then anyway.