It was never a major concern for me - meaning after I bought a Boxster and hoped on the forum and found out the IMSB was prone to failure at about 5% it didn't make me freak. My BMW motorcycles had a 3% failure rate of the final drive and I learned to live with it. Even bought a spare in case it happened to me, but never used it. Once I found the early models had a dual row ISMB and a lower failure rate I stopped thinking about it and just decided to treat it as a wear item every clutch replacement.
I did decide - and got my wife's approval - to buy a 911 so I could drive one while I fixed one. And that removed the worry factor tremendously!
