Re: IMHO it's all a con.
In those cases it's usually been the external wiring out from your house. It gets corroded.
Had many customers call me about their ADSL suddenly failing and nothing internal seems to fix it and BT India are hopeless (always ask to speak to a lLvel 2 Engineer, that does the trick). So I tell them to call out an engineer to check the 2-3 feet of external wiring and that usually does the trick.