There are two parts to that. There is what I call “iron gear”, which can run quite well for many, many years. Then there are things like switches that are a little bit more active and disk arrays that are more likely to break. There are different classes of hardware. They all have a different lifespan and expectation there. In addition to that, the software is accelerating even more quickly, rendering some perfectly reasonable hardware no longer viable because it can't keep up with the processing speeds and requirements.
I don't mean to complicate the answer, but it is variable.