Just clean the contacts with Deoxit and put it in a cardboard box. Leave the tubes in it. It'll be fine. For added assurance, get some silica packets to put in the box (for moisture protection)....just like manufacturers do. As others have said, make it easy to access so you can hook it up periodically and power it up. I think twice a year is the general rule. When you do so, be sure it is connected to a load of some sort, if you don't want to hook it up to your speakers.