Don't do it Tim!!
This is in the same vein as being pressurised into buying 'extended warranties' on goods from the likes Currys, Argos etc. etc.
I always feign shock, horror to the sales person as to why I didn't consider for myself the obvious choice of paying more for my purchase. This invariably results in a huge smile on their face as they move in for the kill. At this point I inform them that, perhaps, as their product needs an extended warranty to give it even a reasonable life expectancy, I should reconsider buying their product and select from a rival outlet. It's amazing how they then back off and can't get you to the till quick enough! And, incidental, I can't ever remember buying anything that would have benefited from having these useless guarantees.