I use it until it's shot.
Really, think about it. It's not being hurt by just sitting there in the chamber. Handling it does not hurt it.
I unload all of my self defense ammo and load with target/range loads every time I go to a shooting session. Then I load up the original SD ammo to carry. I DO shoot all of the clip and use fresh SD ammo about every three months or so.
I've never had a problem doing that.
"We must reject the idea that every time a law's broken, society is guilty rather than the lawbreaker. It is time to restore the American precept that each individual is accountable for his actions." - Ronald Reagan