Hi BGE,
My two were feeding much more often than the formula tub recommended too as I was demand feeding. The amounts they took varied from feed to feed - G was always a hungry baby and used to drink all her formula, M was fed on G's demand and not being half as hungry just took a few ounces each feed! G went through a phase around 18weeks of drinking up to 9oz per feed, but this didn't last long. Generally they were both snackers, taking little and often. It did feel like I spent all day feeding them! Through discussions with various people I wondered if I was feeding them too much or too often, or indeed if I was feeding them each time they grizzled to keep them happy...I did try them with water to try and eke out time, but it made little or no difference. It took us almost 6 months to get into a 4 hourly milk routine and we only achieved that because I started to introduce solids!
Each baby is different, I have always been told it's not possible to overfeed a young baby. It will vary I'm sure - your LO will dictate what he needs