Sleeping through the night...

My son has been a heavy sleeper since birth. I have to wake the little guy up to eat. Hes now 9 weeks old and i still wake him at his 4 hour mark to eat. Can i let him sleep through the night (probebly 6 hours tops) or should I still be waking him? Is there an amount of hours i should/could let him sleep before I HAVE to wake him? Hubby and i are just really tired and dont rest well when we do sleep.