How often do you guys change your blades?

My partner does great work and holds a high standard but NEVER changes is blades! Blows my mind. I had to BEG him to change the blade on his multitool today, I didn't have mine and the blade was literally burning everything I cut with it. He bitched and moaned the whole time about them being expensive and it's a waste of money.

Same thing with his circular saw, jig saw and utility knife. I fucking gave him new blades for his knife after watching him struggle to cut vinyl planking. I don't understand the logic. Just change the blades!