I generally go once a week or once every two weeks. Sometimes once in like four days. All deppends on when I loose it haha...

At College it's generally once a week deppending on how much crap I have to throw in the washer.

My towel is always fine before I wash it, I leave it to dry generally on the back of a chair out of the wash room so it won't get all humid, then I put it back in all dry and moisture free.

I hate damp towels, but yah... there's nothing wrong with using a towel for a few days in a row. I mean how often do you wash your shoes?

It's strictly cultural.