best advice is to change the blade when it doesn't cut. If you do not, you will run the risk of damage to your board.
Good question! I check mine before I start a new project as well as duringmy. Specially if I'm doing a lot of cutting. I always have more blades on hand if I think it's time to change blades. As they say a good blade sharp cuts better than a dull one .
Hugs Edie
I check the screw frequently. Sometimes it gets loose fairly quickly, other times it stays tight.