our LOs were on 4 feeds a day by that age as well, taking about 8 oz per feed .... i think you are doing great!! they look perfect (and mine were doing that same sleeping stint by then too - i think the formula, the 4-hourly feeds, and the structure that inevitably comes with twins were all big factors in that. if it helps you, mine still sleep 12 hours at night and they are 4.5 years old now!!!!!!
welcome to the boards, your guys look beautiful! good job!!!!!!