Fostering?

A lot of the rescues in my area periodically send out calls for new fosters. This is something I'd really like to get involved with, but I'm not sure whether I'd be a good match. Does anyone have any experience fostering? Details on my life situation, and maybe this will help you formulate answers:

I live in a single-family home with my husband. We have no children or cats, although there are both children and cats in our neighborhood and a busy park behind our house. We have a fenced yard with native landscaping (no grass, large bushes and some various cacti, one of which is poisonous to everything - that one is fenced off) and a large veggie garden. It's not a good yard to leave dogs unsupervised. We do not have a dog door.

I work 9-5 Tues-Fri and also 7-10pm Thurs-Sun. I'm usually able to come home for a few hours in the afternoon on Thursday and Fridays. My husband is a freelance musician and works much more complicated hours. He is often home throughout the morning but leaves in the afternoon and doesn't return until late at night. Our schedules do manage to overlap such that our existing Lab, Murray, is never home alone for more than 4-5 hours and we are able to maintain a very regular feeding and walking schedule.

Obviously this schedule would not be suitable for fostering puppies, but what about adult dogs? I don't want to do these poor guys a disservice by my annoyingly busy schedule - they have already been through enough! So, what does the forum think?

Thanks!