idk, after 4 or so uses. I have super dry skin so my towels never get stinky. I’m washing them long before I notice anything. Humidity being very low where I live also plays a part I"m sure.

Some of my towels may be older than me. I got a pile of hand-me-downs from my mother when I moved out and uh….I still use a few of them until they are dilapidated enough to become garage oil rags and then I buy a replacement. Nothing in my bathrooms matches!

Face towels are a different story. I replace them after a single real usage. Probably just as old though.