I bet many of you know this already, but semiconductors do indeed age over time. The article i just linked to is rather interesting. It mentions the fact that chip makers run their processors very conservatively (that is, at a much lower clock speed than they can handle) on purpose to help prevent premature aging, which overclockers and gamers have known for pretty much ever. Heat is also a contributing factor in semiconductors failing over time, but again, most of you probably knew that by now. The article also mentions a bunch of technical reasons for semiconductor/transistor aging that i wont bother attempting to explain here. Apparently the IEEE and a few major semiconductor companies are working on a sort of odometer for microprocessors that measures aging, which in turn will allow the chips to change settings to compensate for their age.
My advice? if you want your devices to last a long time (that is, you are poor and cant afford to replace them every few years) keep them running as cool as possible and do not overclock. Keep the inside of your computer clean and add a few fans if your case has extra spots for them. I also recommend putting ram sinks on all of the chips in your router if you have one, especially if you plan on keeping it alive for a long time.