After I moved out (at XW's request) I did not mow the grass or rake the leaves. For one thing, I have two teenage boys that live there. But more to the point, I wasn't getting any use out of that yard, so I did not feel like I should be responsible for its upkeep.
I'm sure your H's feel the same way. They're putting up with noisy neighbors in the next apt, hauling groceries from the parking lot, coin laundries, etc. Granted, they made the choice to leave, and I did not, but I think the basic concept is, if you are the one living there, the upkeep is your responsibility.
The question of preparing the house for sale is a little different. I did help get the house ready for sale, mostly because there were unfinished projects that I had started. One night I responded to her call about a leaky roof, and ended up spreading a tarp on the roof in the pouring rain at midnight. (Despite the improvements, we ended up not selling, and she still lives there, so all of my work just benefitted her.)
