It's Not Only the Bellows
About ten years ago I installed a LasDrop Shaft seal. It and PSS were rated equal by Practical Sailor. I have not had any problems until the last year and the reason is not the bellows but the alignment of the rotating and stationary seal. No matter how well your engine is aligned, over time the two parts are not going to always be in perfect align. If they are not, then one will wear different and when they are or are not rotating they will leak. That is my problem now. No matter how much pressure I put on the bellows the seal leaks. So it is not only that you have to replace the bellows every five to ten years, you have to replace the entire unit. For this reason I am switching to the dripless packing that has received many good reports as posts on this website. I can fix it when it starts and not have to pull the boat out at substantial cost. No more shaft seal types for me. "Keep it simple stupid" is my motto. Yes, I had good service for about nine years, but the problem comes like all others on a boat, without warning. Now I have pull the boat out and the expense. With the dripless, I can fix it in the water for alot less cost.
