Leave it gassed, the capsules do not seal against rubber so it will be fine.

I leave all of my CO2 guns gassed, maybe not for everyone but I'm a firm beleiver that excessive expansion and contraction is the reason seals fail. I have 23 CO2 guns of all ages, never had to replace a seal.

By all means remove a capsule and store a gun empty if it is empty but the damage is done when removing a capsule with some gas left in it.