Store your piano in a friend's house. I got my start in piano when I was little and our neighbors didn't have anywhere to put their unused huge upgright piano so they let me use it for over fifteen years. They did take it back when we moved because they considered it a family heirloom. We maintained it so it was in better condition when it was returned. Why let a piano site for several years when someone who doesn't have access to a piano could be using it?