In IT, there are two schools of thought on when to replace aging equipment. Most organizations depreciate IT assets over a fixed period of time and replace them when the clock ticks down. But many other organizations, especially service providers, happily ride old, gray-market IT gear until it breaks.
As with many conflicting ideologies in IT, pros on both sides of this divide tend to deride those on the other -- with accusations of running a junky, unreliable network or overspending massively flying back and forth. However, as with most seemingly black-and-white issues, both sides can learn a lot from each other.
Replacing equipment before its time is really expensive