time between feeds

My LO is 5 weeks old today. She usually eats for about 20 - 25 minutes (15 on 1 side, 5 to 10 on the other). I've been paying close attention and can tell she is actively feeding. She wants to eat everyone hour and a half! I know people say to feed on demand and not to stretch feedings, but it's just too much! Is this normal? Is there a way to stretch feedings out in a proper way? Thanks for any advice!