What time does your son go to sleep? I gave up the 10/10.30pm feed at about 8 months old. My baby's feeding routine was 7am milk, 8am breakfast, 11am lunch, 3pm milk, 5.30pm dinner, 6.45pm milk. By 8 months, my baby was having a good enough solid dinner at 5.30pm that she could get through from 7pm to 7am without needing another feed of milk. If your baby is going to bed around 7pm and not waking for the 10pm feed (ie: you are waking him for it) then I'd just try not feeding him at 10pm and see if he needs it. If he is waking at 10pm for a milk feed, then it is probably just a routine you need to change. Perhaps over a week or so you could change to a soy/rice milk bottle and slowly reduce the amount you give him?
Good luck.
SB2