I'm not sure that it is possible to make an old house completely mouse proof so I don't hold much stake with them plugging up all the access points. It is not like squirrels in the eves that can be prevented easily.

What I'm really looking for is their smart placement of baits, which has worked in the past, or perhaps it is just the amount that they use. Either way if I don't get mice for another 5+ years I figure that I'm OK. I think that it has been nearly 10 years since my last batch like this.