Hi, regarding warrenties I would say be guided by your gut feeling as to how reliable your car has been.
Like many here I have had experience of third party car warrenties and IMO they are not worth the paper they are printed on.
Shortly after buying my A4 (just under 3 years old at the time, and bought from an Audi dealer as an Approved Used car so came with 12 months Audi warrenty) the multitronic ECU failed. I called the dealer fully expecting the 'usual' fob off. I couldn't have been more wrong, my car was collected within the hour, I had a replacement car within 2 hours and my car was repaired with no quibbles and at no cost to me.
In the remainder of the warrenty period the car broke once more (ECU settings) and I had to call out Audi-Assist a further 3 times (faulty brake light switch, cracked fuel filter and cam lifter sensor). As Audi rarely seem to have parts in stock my car spent 8 weeks off the road in my first 12 month of ownership.
Now, I am not at all happy that a car I bought primarily for it's reputation for reliabilty should turn out to be a lemon.
But the fact remains that all of these issues were fixed at no cost to me and I have had loan cars supplied to me within 3 hours each time. I have guesstimated that if I had pay for the repairs myself (obviously not at an Audi dealer) then it would have cost me around £1500. But the killer would have been hiring a car whilst mine was off the road. I need to travel 100 miles a day, I have no access to another vehicle and public transport is a non-starter for my route. I could easily have spent another £2000 in hire cars during this time and I certainly wouldn't have been trundling around in decent cars. In total I have done over 4000 miles in the loners, mileage that I have not put on my car.
So when it came time to renew the warrenty, it was a no-brainer for me. I renewed. I was not happy about having to shell out over £800 but the alternative was to change the car, something that would cost me lots more; frankly money I don't have at the mo.
Two weeks later, car broke down again, fuel sender / pump this time, two weeks off the road and a new A6 2.7TDI Avant as the loner this time
So, the purpose of all this is to let you know, I have comprehensively field tested the Audi warrenty and so far it has not been found wanting. But it should be fairly obvious that for me the decision to take out a warrenty was pretty clear cut as my car has proved troublesome.
If your car has proved generally reliable, I would put the warrenty money in an account and save it for any repairs. If you get no probs you've then got a nice little pot towards your next car