The supply is not the newly minted coins, it is the coins that people decide they do not want to hold, miners and normal beings alike.
Indeed. At a certain point, most coins should become "liquid" again. A store of value which is never claimed doesn't make sense.
Everybody storing value for a purpose, needs to use that value some day, otherwise it doesn't make sense.
Keeping forever is the same as loosing the stored value. It would be equivalent to "hide" gold on the bottom of the Atlantic ocean by throwing it overboard, by burning fiat, or by erasing your private keys.