The first thing to keep in mind is that one of the key things that our air force focuses on is flight safety. We try to minimize the risk and ensure that we're only putting safe airplanes into the sky.
However, I think the basic point you're getting at is that when you have aircraft that are trending towards 50, it takes a lot more effort to keep them serviceable. You can do it. Canada has, unfortunately, shown that we can keep very old pieces of equipment serviceable for decades past their appropriate service life. It's a function of how much time, effort and money you have to put in to keep doing that, and we'll have to put more in as they get older.