B.,
I would keep going over to breastfeed as long as you can. Practically, it will keep your milk supply up so you can continue breastfeeding. Pumping does not provide the same amount of stimulation for your breasts, so while many mothers do very well at first, most moms who pump breastmilk stop doing so by the time baby is about 6-9 months old. The longer you can breastfeed your baby, the better his health (and yours!) will be. Emotionally, this also provides a great time when you guys can reconnect. It is very stressful for a baby to be separated from his mama. While you have to do what you have to do, these nursing breaks reassure him that you are there for him, and can also keep you from feeling disconnected from him during the day. As another poster said, nursing is about so much more than just getting food in the baby - it is about comfort, love and connection, and that is something that cannot be replaced.
As baby gets older, he will be able to be apart from you for longer periods. I know this tiny baby phase is INTENSE, but it does not last forever. Before you know it, he will be happily waving goodbye to you as he runs off to play!
Best,
S. L