Formula feeding moms: When did your baby stop night feedings?

my twins are almost 5 months and they get up every 1 1/2 to 3 hours every night and they are formula fed, but i would feed my baby as long as it can . i know it is very tough and tiring but at the same time it is the best thing you can ever give or do for your baby.if i could i would but i had problems so i had to stop and give them formula. i am jealous of all moms who feed. GOOD LUCK!!