What's in a warranty? And what should you expect when you service an old computer?

I've put a fair amount of brain-time into replying to this thread on macrumors. I feel like it's worth tossing on the site. Several arguments are going on here, from whether it is ethical to have a short warranty timeframe, whether you should expect an older Apple device to fail post repair.

The thread is essentially my reply to someone who had their device serviced elsewhere, and my thoughts on his criticisms.

My thoughts in a nutshell

• If it's an Apple motherboard older than 4-5 years old, you may be better off keeping it dead.
• Ask about the warranty, what is covered, what is not, and what type of service to expect post-warranty prior to purchasing a service.