X2 on the 303 Aerospace. Used it for a LONG time. Since using tires past 7 years is dangerous, keeping the tires clean and sprayed with 303 will keep them looking so good people will question why you are buying new ones (at 7). Have never covered my tires and they always look as good (or usually better) than ones that have been. You will not see cracks on your tires before 7 years (can't attest to beyond 7 since I will not keep them any longer than that) if you follow that regime. I question the 'rotting from the inside out', I think the deterioration is equal throughout the rubber..just comes with age. Rubber begins to deteriorate the moment it is made. Little cracks on the surface mean nothing and are just from ultraviolet sun damage that the 303 will prevent.