Many museums have a membership. For one price you can visit the museum any time you want. I strongly recommend everyone do this for all their local museums. It changes the experience when you don't feel bad about wasting the admission because you only have an hour. Particularly small local museums where spending all day isn't worth it, but if you have to pay admission you feel compelled to spend all day to get your money's worth.

Some of them also include reduced price admission to others of the same time. My local zoo isn't very big, but the membership means half price admission to a very good zoo just a couple hours away. My local science museum got me free admission to many other science museums and children's museums. My local historic farm got me into a lot of interesting historical sites. Be sure to understand what you get and take advantage of it on vacations.

I strongly recommend you get the version that lets you bring two guests. When my parents or some other friend from out of town comes to visit we have something interesting to show them (and if they are not having fun we can leave early).