If you stay in a bath for too long as in longer than 30 minutes then your skin can become wrinkled and then your skin starts to break down the longer you stay in the bath.
When I soaked in a bath for an hour I really started getting my skin wrinkled so I now no longer stay in a bath longer than 30 minutes.
Your skin will return to normal after you get out of the bath but it can take a few days or so to get the wrinkles out of your skin.
You basically dry out your skin when staying in the bathtub too long.
You're not gonna really be harmed when you stay in a bath too long but your skin can get wrinkled and eventually you may have permanent wrinkled skin.
So avoid staying in the bathtub for longer than 30 minutes and use a skin moisturizer to moisturize your skin after you get out of the bathtub and dry off.