I just went to see a WW in NC and it has been in an unheated attached garage for 10 years. No planking at all and the playfield was as good as you will see on a WW. I have bought a lot of machines from Operators that don't have heat or air in their warehouse and none have planking. I have machines in my garage off and on and they are fine. Maybe it happens in the North where the winters are colder.