When designing an exhibit you should always assume that at some point it will eventually break or require some kind of maintenance. Exhibits endure a lot of abuse. If you are a designer you should always take into consideration that someone else will need a clear and easy way to maintain it. Don't cover screws with wood putty and don't build things that are so heavy they're impossible to lift. Try to use parts that can be bought off the shelf. For example; don't install a light bulb that needs to be specially ordered from Germany. One day that bulb will need to be replaced. The person responsible for maintaining the exhibit should be able to simply open a door and unscrew the bulb to replace it with a new one. It should not require five men to remove the exhibit from the museum floor with a forklift or hiring someone who speaks German to call the company in Germany only to find out they are no longer in business.
It's also a good idea to leave enough storage space under/behind your exhibit to store extra or spare parts. This will help avoid having to put up one of those dreaded "out of order" signs that cause visitors to complain about all the money they spent to see broken exhibits. If any pieces of the exhibit somehow disappear (as they often tend to do) they can be quickly and easily replaced. This will make the exhibit maintainer's job easier and more efficient and the museum visitors will be much happier when the exhibit is working.
