I have a minimum 3 day booking, 1 guest only, but most of my guests stay for a week-2 weeks. I leave a guest 2 bath towels, a hand towel and a washcloth and offer fresh ones at the one-week mark, but my guests tend to be the environmentally aware types, so they usually say they don't even need clean ones after a week, maybe a clean hand towel amd washcloth.
Women with long hair tend to use one towel to wrap around their hair if they have washed it, and one for their body.
Myself, I go 2 weeks on a towel- if you just use it to dry off after bathing, and hang it up to dry, it's still clean, right? It blows me away that people will use a towel only once, throw it on the floor and take a fresh one off the stack for the next shower. I was co-hosting for my neighbor and his 2 male guests went through 17 bath towels in 6 days.
I also ask guests to bring their own beach towel, as those get run over by kids and dogs at the beach, are filled with sand, and can often get slung over a chair at a beach restaurant and forgotten, especially after a few margueritas 🙂
But with the tinier and tinier luggage restrictions on planes, I know guests don't want to take up space in their luggage with towels, so have a couple non-luxurious beach towels to offer them if they are just traveling with a carry-on.