You don't have to buy a back up. I choose to buy one. The reliability of earlier T300's along with setting 100% Force feedback on PC1 and PC2 led to over heating, which in turn effected the motor. Currently my wheel FFB is set to 70%. At that FFB I have plenty of feeling in the wheel. Thrustmaster has since given an option to allow the fan to be "on" at all times which aids in the cooling and increases the longevity of the wheel.
You don't plan to smash up your car, however you buy insurance. I do not plan for the wheel to break, this purchase my insurance policy.
As far as who has the most reliable wheel, there are already enough threads open discussing this matter and I do not feel we to start a new one.