For All Of Us: A Great Message!

Question(s), please.
How often do you need to change an N95 mask? When should you dispose of one and wear a new one?
A public health nurse gave all of our staff a mandatory masking lesson. She said the paper surgical masks (white on one side, blue on other) were only good for about 30 minutes, that once they were wet from condensation (your breath) they were no longer effective. We were told to never reuse a mask, unless it was one that could be laundered. I know some people just keep one crumpled up in their pocket and they pull it out for use repeatedly, days in, days out. (Another good reason to distance).
It would be good for people to know the difference between good masking and ineffective masking.
Thanks!