From my experience, I'd have to say fork seals weeping. Mine had a slow weep and fork stanchions were a bit out, so got new stanchions and seals. I am now going for my 3rd set of seals from motorworks for an unknown reasons. Installed by 3 different specialists so its not me bodging it! Only thing could be is that they need to be OEM. As for that, never been stranded or failed to start and stop in 3 years now. Bike stands outside all year and has been left without charge (3 weeks one one occasion)
No different to a 1150gs as same motor. Had a new clutch at 35k too but that was me being prepared rather than necessary