I've been curious about this for awhile now. I don't know if I'm seeing a real pattern or not, but having worked with many home office/small office wireless routers for a few years now, I've noticed that the heavier the traffic is in the environment, the less reliable they become over time.
Desktops become clogged with malware and innumerable user installed programs, but a router just sits there "untouched" - pretty much the same as the day that you pulled it out of the box - other than occasional firmware updates.
I'm not talking about total failure, but the frequency that they become unresponsive. A quick reboot and users can connect again, but over time those reboots happen 3-4 times/wk rather than once a month or once every 6 months.
I guess typically over time bandwidth demands also go up - more users connecting or downloading/streaming more things, but in a couple environments where usage rates stay relatively constant, it still seems to happen.
I would think that the hardware would basically either work or not rather than a general decline. What components, hardware or software, might be causing this or is it a made up pattern in my head?
Edit: Not to make this question more complicated, but sometimes it's just the wireless access that stops. The wired computers continues to work just fine. Hopefully, some others can confirm that they've seen this, too.