Five month olds eat every two hours?!

I nurse on demand. My five and a half month olds (twins) want to nurse every two hours, and the longest stretch they go is around six to seven hours at night. They have one long stretch like this at night and medium stretch around three or four hours. The rest of the day, they are eating every two hours, and sometimes even want on every hour as the evening goes on and they get overtired because they have to nurse to sleep and they just can't seem to fall asleep and stay asleep

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Is this normal? I was hoping by this age that they would go for a little bit longer throughout the day.

This is not a recent development either, this is their every day routine.