Cooking the mask ensures that microorganisms on it will die and not pose a risk to the wearer. A mask sitting around for several days can still harbor them in some cases.

I see that in general, but if we're wearing N95s specifically to protect against the coronavirus then several days seems like it should be (a) enough and (b) not as hard on the mask?

This is what I do. I just place it in a plastic bag and don't use it for about a week. I have enough to let me use one each day and quarantine the used mask for a week.

What's the plastic bag for? Seems like a good way to promote bacterial and fungal growth.

I'm using open plastic bags for avoiding touching the mask itself. I figure there's enough air circulation when I let the bag sit open on a shelf. Granted a paper bag could be better.