Yeah, it's a good idea to buy a couple of brand-new tail motors whenever you upgrade to a dual tail motor mount, even if the previous motor isn't very old... It doesn't take long at all to wear out a single motor on a LiPo-powered HH gyro setup. If one motor seizes or otherwise locks up, then it will quickly overheat the other and then both motors are shot. But if both motors are brand-new, then both will wear out relatively evenly and you greatly reduce the risk of frying a good motor because one of them was old.

I have a dual motor setup for my CP Pro tail and I bought two new tail motors for it, and I've run it well over what a single motor is expected to live. It rocks! Buy two motors and see if that gets you back in the air, and if it does then you're not gonna be buying tail motors for quite a while.