It's rated for 4 hours battery life as per DJI spec. So assuming you land with ~20% battery left like most people, that is about 25 minutes per standard battery or about 9.5 theoretical flights before you have to charge the RC. You don't want to run the RC battery down to zero as that is just as bad for it as it is for a drone battery, so it's more like 6-8 flights.
If you aren't using the RC in airplane mode and have the screen brightness maxed, and are using it to record to a SD card of it's own, I would expect noticeably less battery life.