Thats been about it for us. It's not a sudden dropoff or catastrophic failure, but you can start to see obvious signs of degregation. Little more smoke/haze, dirtier hull, sheen on the water etc. After 12-1500 I'll change them out on the next downtime cycle.
In the last maybe 8000 hrs total run time I've only had one catastrophic set of injectors failure, and it wasn't their fault. Going thru regular routine I transferred fuel from a storage tank into the day tank, unfortunately there had been a leak in the storage tank top and probably let 20-30 gals of water in, it went straight to the bottom of the day tank and within minutes I had pure water running thru the Racors, booooommm. Lights out.
A lot, a lot of work to fix, a lot!!! We were at a small resort island in the Bahama's so had to do it all ourselves. Couldn't move the boat or even start any other engines because day tank fuel was contaminated. All new injectors, new fuel pumps, new primary and secondary filters, Racors rebuilt, two guest cabins torn up to access the fuel tanks, inside the tank cleaning, and multiple passes of polishing over 5000 Gal fuel over and over again. Then had to find and fix the leak that caused the problem in the first place. Put it all back together, get carpets re-stretched, and had ozone machines flown in and ran for months to get rid of diesel smell. All this on top of our normal busy workload. Ahhh, yachting, isn't it funnn!!
Cruising=Repairing your boat in exotic locations.
Or, in our case, getting paid to repair the boss's boat in exotic locations, while other people are having fun, and telling you how nice it is and what a good time they're having, lol.