Seems like a lot of formula to me. My son is 4.5 mos and we just bumped him to 7 ounces. When he was 7 weeks he was taking 3.5-4 oz bottles.
How much does your LO weigh? A good estimate is to take his weight and multiply it by 2 or 2.5. That is about how many ounces your LO should be taking in 24 hours. So if he is 10lbs, he should be taking about 20-25 ounces.
But, if your LO is handling it well and not barfing any of it up, I guess he needs it.
EDIT: I am a total idiot. My mind switched the numbers around and I though you said you fed him 8oz 3 times a day. LOL I was like "Woahhh..."
I would try and bump him up a half ounce and see how he does.