I think 5 minutes per side every 2-2.5 hours during the day, and every 3 hours at night, for the first day or two days sounds totally reasonable, until your milk comes in... Then once your milk is in and going well, you should be able to do every 2.5-3 hours during the day and 3-4 hours at night.
Every young baby is different. Some will feed for 10 minutes every 2 hours with barely any interval for long blocks of sleep. Some will want to feed for 30-45 minutes every 2.5 hours. Others will have a longer block of sleep of even as long as 6 hours in the first 24 hours after birth. But then wake up and be keen to feed after that.
Mine are one of those 40min feeders
Kate x