In a perfect world all flashlights should be checked rehularly, perhaps monthly.
In the real world however this gets neglected.
A compromise might be a number of cheap basic flashlights fitted with new fresh alkaline or lithium cells.

Premiun alkaline cells are warrented good for 7 years from production, so if fresh when purchased should be good for at least 5 years storage.
Checking for leakage or other failure would be prudent just in case, but they should be fine if neglected for 5 years.

Lithium cells are warented to be good for about 15 years from production. If fresh when purchased they should be good for at least 10 years storage.
Again it would be best to check them, but if this is neglected they should be fine after 10 years.

At work I keep about 20 cheap basic flashlights as loaners.
Most are 2D rubber ones with a 0.5 amp incandescent bulb.
This gives enough light for most purposes and gives a run time of 25 hours from alkaline cells.

I do of course have better lights for my own use, but for lending , the cheaper and simpler the better.

Flashlight technology is improving rapidly and I would urge that those who chose to upgrade to the best/latest types should store the old ones.
You, or somone else might be glad of these in an emergency.