Just serviced one of my J7 levers due to small leak at the reservoir cover (fluid weeping out at the edge of the cover when brakes applied). Replaced the reservoir element (rubber piece under the resevoir cover) as it was likely that this was perished (18 months old) from previous posting discussions. It all appears to work now it's rebuilt but on examination of the old element it is in good condition with no holes or signs of persishing. Its still extremely pliable and like new. The only thing I can see on close examination is a small moulding mark on the edge of the seal area where it could have possibly caused some fluid to leak past? (if so why did it last 18 months before giving up?) Anyway - it looks like its fixed so no big deal - just thought I would share it with you all. I bought a lever rebuild kit to get the new parts (UK money about 6 quid) and it takes 10 mins to swap over as longas there is still plenty of fluid in the system.
Cheers, TonyG.