We have 6 years experience with ours. Quite pleased with it.

I just took it off to check the rubber sleeve. It is A OK

You certainly go to town on securing the collar.
One thought is that it is occasionally necessary to move the collar to compress the rubber more. If the shaft is dimpled, that could cause a leak along the shaft.
Given the cost and work involved in replacemnt, I hate to damage a prop shaft.
Ours collar has never moved, using the standard PSS installation.
Having said that, I just had it off, so we will see what happend after launching (today)
I suspect any collar movement would cause a small leak initially. Experience from others would be interesting.
I think I will add the collar, using a zinc. Ours fit the shaft well

I often wondere about the danger of the rubber sleeve disintegrating. I guess we coud wrap it in a cloth and tie it tightly, to limit leak to small amount.
I have thought of making up a "bandage" for the job, but have never done so.
Has anyone a backup for the rubber sleeve on PSS, or any other floating seal ?
The PSS rubber looks better to me than most that I see.