I was fortunate enough to have some unused N95 masks left over from the Sonoma County fires from 2017. So far, I’ve only used one mask during the COVID-19 pandemic. I leave it in my car on the passenger seat next to the Clorox Disinfecting Wipes. For the few times I go to Costco or other rarity, I wear it then and try to get in and out of the store as fast as possible.
As far as I can figure, unlike smoke particulate which can clog up a mask, coronavirus is damn near invisible and dies on surfaces after a only few hours - certainly will be long dead if left in a car, exposed to sun for a week or longer. So I don’t see the logic in throwing out a N95 mask that might have dead virus on it until it starts showing signs of wear, which so far this one has not and it’s been the one and only mask I’ve used since March.