You can use your towels 3 to 4 times, but then they really need to get washed. Towels are designed for heavy use, but they will start smelling after only a few showers. Especially if you don’t let them air. Make sure you hang them out after use, so they can dry up quickly.
If you work out or have a physically demanding job, wash the towels more frequently.
Also, don’t share your towels with family members, if someone may have an infection, as towels are an easy way to bring that infection from one person to another. Especially when the towel stays even a bit humid.
But don’t hesitate to replace a towel, when it’s time is up. There is nothing better than a brand new, fluffy towel. And even though timely washing will keep that freshness and softness. Eventually it looses its magic and it’s time to replace it with a towel that makes you super happy as soon as you pick it up after your shower.