[Arran]

 The main issue with early solid state devices is the small electrolytic caps drying out with age more so then leakage, this is something that is more dependent on how the device is stored then how much it is used. On occasion, especially with 1960s era solid state devices, you can end up with leakage between the elements, instability, and even tin whiskers causing shorts, though I haven't heard of that being a problem with these TVs as yet. The other killer, as Brenda mentioned, is battery leakage, but that goes for battery powered tube stuff as well.
Regards
Arran