You appear to reinventing the wheel. your clients are older and you are wasting a lot of your energy and their money to do something that isn't necessary. DVD players are a commodity, I doubt leaving it on is going to cause any problems. Whats the downside? A service call in 5 years maybe more to install a new one.

There are situations where simplicity and common sense make the most sense. As installers we are wired to solve problems and sometimes we create problems for ourselves.

Keep it simple and reduce callbacks at your expense.