For $4000, I would not do it for another 2 years of coverage given the mileage you drive. Keep track of your costs over years 5 and 6 and I think you will come out ahead. Paying for a warranty is sort of like buying insurance.
If it was $2000, I would seriously consider it. At that price, if nothing else, it would help the resale of your car should you decide to sell it since many buyers with no experience with the car feel safer with some warranty.