If it's managed to keep running for over 40 years, then it's good to go as far as I'm concerned. At this stage, a C-12 is just as likely to fail as a C-11 really and both will need some care and attention every few years to keep them working well. Many of the parts are interchangeable between the 2, but parts availability will become a thorny issue for both - I suspect we'll all start stockpiling off-brand watches using the movement for spares before too long.