the life span of a router

On average, your router has a life span of about 3 years.  That doesn't mean it won't live longer than that, it just means that after about 3 years your router is now out of date.  Technology changes so fast that the range and speed will be slower and have a harder time with more devices ie. computers, printers, cell phones, etc.  Additionally, the more devices that are being utilized, the more noise there is for the router to try and deal with daily.  Newer routers and wireless adapters can accommodate all your devices and take care of that interference for you.  For example, I have a very old Netgear router (5+ years old).  When I upgraded my computer set-up, I purchased a brand new wireless adapter to minimize the interference.  So far, all are working well!