Source for rubber stuff that lasts more than a month

My hand brake gaiter has just split at around 13 months. Today I ordered a rubber drain coupling because I have to join a terracotta drain to a plastic one on a burried drain - its rubber and 5" dia x 3" long and about 3/16 thick so its about 2x the rubber as the gaiter and it was £9. Becuase of its use it probably has to last at least 25 years so its not even price, its about bothering to make a decent product.

I've just replaced my Hi-Lo lever gaiter; it was a Britpart bit and it lasted about 4 years. I had greased it inside with ordinary yellow grease and sprayed the outside with silicone lubricant, idea being to keep the oxygen away. This time I used silicone grease on the inside of the new Britpart gaiter and the silicone spray on the outside again; time will tell... I should say: the 'new' part is in fact also 4 years old, I bought a few spares, it seemed to be in perfect condition, kept sealed in its bag and away from the light in a box.