Depends on the condition of the pants. I am still wearing some that is 15 years old.
You can use a diaper pin to fish a new string over it, or even better get elastic bands (not sure what they are called), fished over the same hole and then stitches both ends together or to the pants.
If you have no time just donate it and get new ones, they starts at around $10-15.
I have several pairs of sweat pant that have had the tie string at the waste break.
I'd like to hear your thoughts on fixing the problem.
New string, attach it to a long thick needle, a small screwdriver, or a custom piece of wire coat hangar. You can use a safety pin as mentioned.
I like the paracord idea, that won't break for a long long time if ever.
He never stated that he wears them out in public, maybe he likes to wear them around the house... He asked a simple question.
Even if he does wear them out, so what?
Don't wear sweat pants. People who wear sweat pants and clogs/dogs in public scream "I've given up on life."
In all my travels I've noticed Regina and surrounding areas have the highest concentration of people who commonly wear them.
Only time I wear them is to the gym when it's too cold to walk there wearing shorts.