Experts recommend that you wash your bath towels after three times.
As a general rule, towels should be cleaned every three to five uses according to Bed Threads.
These experts then discussed other reasons why towels should be changed regularly, including drying time and whether they are able to withstand repeated use.

Experts advise that bath towels should be washed after each three-uses.
“Hang the towel somewhere that is ventilated, and let it dry thoroughly before you use it again. They recommended that it be stored somewhere outside of your bathroom.
You should not use your towel if it is damp. This could lead to a growth zone of odour-causing bacteria.
This bacteria is at home in dark and moist environments. Dead skin cells are an added bonus to the colonies’ rapid growth.
Experts also pointed out that the type of towel used around your home could impact drying times.
The traditional, thick-pile, cotton towels for bath should be washed the most frequently as they are more difficult to dry than those made of lighter materials.
If someone is unwell, experts recommend that you wash all towels in the house.
Their recommendations were also supported by the Cleaning Institute who saw towels for three to five more days.