So long as you don't mistreat it, there are really three caveats to proper usage of a device down the road-
The Battery
Even the newest batteries don't last forever. Depending on how many times the device has been charged/discharged over the years, the battery may no longer last. Simply being in storage would prevent that, I imagine, but we don't have a measured description of how much usage the device would receive over the course of the years being described, so we have to consider both options.
The Storage
All storage methods have a finite lifetime to them. If your tablet is being used constantly, bear in mind that every write cycle reduces the lifespan of the internal flash memory by an infinitesimal amount. This of course would be negated if your device is in storage, because no read write cycles would be used.
Time Moving Onward
Depending on how you want to use your device, you may find it difficult to use the device a long time down the road. App stores will close, the companies that provide network services will discontinue those services, replacement parts become unavailable and so on. If you stick to local apps, so long as the device doesn't demand an update it cannot find, the apps should still work.
And of course it begs the question- will it still be useful a decade down the road? Technology is moving at a blistering pace; what once was cutting edge is now ancient. How useful, for example (except to collectors), is an Apple Newton, an HP 600LX or a Mac Performa 450?
Just some food for thought.