With time it happens on every unit and in most lines -- a minor leak at the junction between the hose and a device. For example, a leak at the base of a vacuum valve or where the tubing connects to your handpiece. Over time, tubing gets stiff and brittle and can develop pin holes or even begin to crack.
Fortunately, it is often just at the fitting that tubing wears so. Tubing is usually held in place by being stretched over a barbed fitting. If you have a leak in your hose at (or near) a connection, normally you don’t need to replace the entire hose. You can just trim back the hose and re-attach it.
Much as with rusty metal or cancerous tissue, you want to cut back enough to be assured of “healthy” tubing, so cut the hose 1-2 inches back from the problem area so you have “fresh” hose to re-attach. Most lines should have enough slack that losing a couple inches will not impair usability. Before sliding the fresh hose onto the fitting, dip the hose into hot water (as hot as fast food coffee) for a few seconds. The heat will soften the tubing making it easier to slip over the fitting. That’s all there is to it.
Everything wears out and tubing usually needs to be replaced every 5-6 years, but the occasional minor leak can often be fixed without replacing anything.