Pumping

Did anyone on here pump more than breastfeed? I'm wondering because my baby is a preemie and is having a hard time latching on he will only do it with the nipple shield and it's only sometimes that he wants to try and suck using it. So I pump and bottle feed him. I'm wondering has anyone just mainly pumped and how long did you do it for? My goal is till he's six months I have a lot frozen also, I produce quite a bit of milk.