As a teacher, I think we have to expect that our students will use the internet if they have the opportunity to do so. If you want to reuse old questions, give the test in class, so that internet usage can be controlled. If not, then use new questions each year, or a different combination of questions.
I know it’s easier in math than in history, but each class gets a different version of my tests. So knowing the answers to the 3rd period test won’t help the kids in 9th period. I think it provides a more level playing field.