Got my amiga 500 down from the loft about a year ago. It had lay dormant for at least a decade. Plastic had yellowed. I plugged it in and turned on the power switch, expecting to hear a fizz/pop and declare it dead. It booted up fine. And ran kick-off 2.
Seems the only thing to degrade in those 10 years is my reaction time.
Assuming you're hoping to play more Kick Off 2 (plus a bit of Sensi perhaps ;-) ), it's highly recommended to replace the capacitors, as leaking capacitors have a nasty habit of ruining old computers. Also, regarding "Plastic had yellowed.", you may be interested in this...
https://en.wikipedia.org/wiki/Retr0bright
Seems the only thing to degrade in those 10 years is my reaction time.