How often do you change your razor blade?

I'm a Male who doesn't have a thick beard or much facial hair. At best, I get a small stubble on my cheeks, where my moustache can grow a bit more. I can easily shave my cheeks without any cream or prep, moustache I'd generally have to soften up the hairs for a good shave.

Generally, I use the razor for a few "shaves" which can last a few weeks. Since there isn't much hair, it doesn't dull as easily. I'll change it out after I feel its getting slightly dull or when I realize that it's been a while since I last changed it.

Curious as to what others do or if there are things I'm potentially overlooking (e.g. hygienic reasons to change more frequently).

Also - I recently switched to a single blade, straight razor.