How long should my daughter be feeding?

Ta
My daughter is 6 weeks old and is exclusively breastfed. She will also go up to 4 hours without eating. Even if I try to force her awake. She isn't running any fevers. Doesn't seem to be getting sick. She does have really bad reflux, and is on medication fot it. She only feeds for about 10 at a time, But Sometimes as little as 8 minutes. How long should she be eating for? What is normal and what isn't?