It depends on how hot it is, how hard I work, how much I sweat. If I have to have three showers a day, then I put on clean undies after each shower. So, a minimum of once a day, and no telling what the max might be. I have on occasion had 5 or more showers, in one day.
I change mine depending on what I have to do in the evening. I always wear a fresh one first thing in the morning and that comes off when I go home. If I have to go out then I use another one, but I may use the this same on the following evening too. It is the length of time that I have been wearing that counts. I have a change of underwear in my car for emergencies along with a pair of jeans and t-shirt. There are times when I have changed my underwear thrice If I have been wet with pre-***. this can happen.
Just depends on how you fill and what you're thinking off
Depends what Im doing tbh :-)
I don't usually wear any, or pants in hot weather