There are two parts of the question:
1.How long does an N95 mask lasts?
N95 masks remain effective far longer than a single day. This data suggests masks can retain fit effectiveness up to the point masks become so gross and hard to breathe in that most people would want to throw them out anyway. Or usually the strap of the mask would break so you have to get rid of it.
2. How to disinfect the mask after per use?
The simplest method of all is to channel your inner zen and do nothing! If you have a few masks, then simply leaving masks to dry should cause viruses to lose infectivity in 48 hours (72 hours would be even more conservative: 1, 2).
For more details and references, see here: https://www.quora.com/How-many-times-can-an-N95-mask-be-used-before-it-becomes-ineffective-against-the-COVID-19