How long should an HW break barrel breech seal last

[TonyL]

What lubricant do you use?
Could it be deteriorated by lubricant?

I did wonder that, but the breech only gets an occasional wipe with Parker-Hale Express Gun Oil.
.

Obvious answer would be stop using it, or change to a different product, & see if it makes a difference, a good wipe of silicone grease, just to the rubber seal, before fitting might help a bit.

Normal gun oils are made for metal lubrication and preservation, not lubrication of synthetics.
Wrong lube seems to be the obvious problem here.

Makes sense.