My DS was doing that too at that age. Its a little unusual for a BF baby, but if he's happy with that and gaining, wetting enough nappies, etc. go with it. Length of time between feeds is usually 3hr when on 3hr EASY (1.5 A, 1.5 S) and 4hr on 4hr EASY (2hr A, 2hr S)
What does his daytime routine look like?