Formula feeding/bottles per day

Da

My son is 10.5 months old, has been formula fed since he was about 1.5 months old. He has been getting 4 7 oz bottles a day (28 oz total) for quite awhile with 3 meals and 1-2 snacks a day. Sometimes he'll leave 2-3 oz in a bottle or two a day. I'm not sure when/if I should decrease him to less bottles a day. Any suggestions?