Newborn Visitation

Ch
My baby is just over 3 weeks. Dad and I aren't together. He has been visiting over at my home just about daily. We had a talk yesterday as our relationship had been pretty odd, but I'm tired of fighting for us or trying to save or salvage what could be, we decided he could have visiting time at his moms (where he lives since we split) so that way he doesn't have to only visit with me around at my home.
-It's his first baby.
- she's exclusively breastfed 
- I haven't been able to pump much this pass week. So she nurses on me .
???? My Question ????
How many hours should I leave her over there? 
Let me Add that while she does have bottles I can send over with her there is not a lot meaning 6+hrs would be too long.
-Trust he when I say he's not gonna give her formula 1- because he thinks she'll get sick (even though she most likely will not) 2- because then he believes that will require him to purchase more milk for other feedings...we agreed before that breastfeeding was not only healthier but more economical for both of us.