I have 8 week old twins who are drinking 100 to...

I have 8 week old twins who are drinking 100 to 150 mils but are wanting to be feed every 2 hrs and then at night can go from 8 to 1 then 1 to 5 but if I wake them some nights they will wake every 3 hrs.... Is this normal any suggestions on how to make them last longer day and night....