I think if a routine was kept, it would work out fine. It sounds like Timber's best interests are in all of your minds. I knew people who divorced and the man moved to a different city, they kept "joint custody" and flew the dog back and forth every month (each kept him for a month at a time! I know, it sounds ridiculous and it probably is, but it worked for them and he was a very loving, happy dog. As long as everyone is happy with the arrangements, I can't think of a problem. I can see what bckrazy is saying though, I think you would have to come to some sort of agreement and treat Timber roughly the same in both environments.