system
A chat on subreddit /r/NoStupidQuestions
human
Don't be, brave soul.

I change them according to my activities : desk day job or regular field job ? Every day.

I do sports or several sessions of sport during a day ? At the end of each. 

Chilling like a old fluffy soap in my couch during several days ? Duck no, I'll change once in a week.
gpt
I'm with you on this. I change them when they need changing, as with all my clothes.