There's no clear-cut answer except: When your baby is hungry, feed him. Most babies want to nurse irregularly at first. It might be every hour or even half-hour for part of the day with one long four- to five-hour sleep stretch, so you'll have to watch your own baby's cues. You should feed him as often as he's hungry — even if you feel like you're feeding around the clock. And go ahead and wake him up for a feeding if he sleeps past five hours in the first few days. Breast milk is digested pretty fast — much faster than formula — so breastfed babies will be hungry more often than babes on the bottle. Eventually (within a month or two of baby's birth), your milk supply will build up, baby's stomach will grow, and baby will learn to nurse more efficiently — all factors that will probably stretch your time between feedings.
After that first week, it's okay to let your little one snooze for up to five hours in the night without feeding (if you're so lucky), as long as he's eating eight to 12 times a day. And after about four weeks, you're free to let baby sleep as long as he wants at night, provided that his growth is on track.