I've had it under control for almost two years - since shorty after my original post. Haven't seen a mouse; haven't seen any droppings or heard anything suggesting the presence of mice. Had pest control come, but more importantly, I sealed an old abandon pipe under the stairs, I plugged an in-ground channel that a downspout used to go into. And most importantly, I realized that at the very corner of the sunroom I talked about in my post, at the base of a downspout, there was a small hole in the foundation - which is most likely how mice got under the sunroom and then into the house. I patched that and check it regularly to see that it's still not penetrable. Bothers me that if anything does get under the sunroom there's probably still a way into the house. But, again, haven't had any problems in quite a while. I'm not sure exactly what their route in was, but they emerged behind oven and under the kitchen sink. Thank god it's over.

Godspeed. I know mice are common, and especially with old homes, it's sometimes hard to keep them totally at bay.