Many pediatricians think there's optimal value in allowing feeding more or less on demand for the first several months. It actually sounds like your son has found the rhythm that works well for him, and since he's only waking once at night (lucky you!), and he's apparently thriving, I wouldn't make him wait between feedings long enough to get desperate, at which point there could be physical and emotional implications on into the future.
When my daughter was born, shortly after the invention of the wheel, the standing "rule" was that babies should be trained to feed only every four hours. My pediatrician actually bawled me out for feeding every 2.5 hours, so I really tried to get her to adapt to the 4-hour schedule. She simply couldn't do it; even though I had plenty of breast milk, whenever I coaxed a few more mouthfuls into her when she was obviously done, she always spit them up shortly afterward. There was no way her little tummy could contain any extra milk. And the misery we both experienced when she was hungry and I tried to make her wait was intolerable.
So I went back to her schedule, which extended by itself over the next several months. We were both happier, and the doctor, who never heard about my subversive activities, had only glowing things to say about her health and overall contentment.