I put over 200,000 miles on my diesel Rabbit. Never had any leaks. Only corrective engine maintenance was to replace a glow plug. Added gasoline, about 20 to 25 % to the fuel during cold weather (20F and below). It would get to 75 MPH on the Interstate with no headwind, and still get 55 MPG.I have no idea how much actual difference there is between Jet A and diesel fuel, nor how long it would take to damage an engine. You couldn't run it in anything that has to have an inspection, since it won't pass due to the higher Jet A sulfer content. I do know diesel has lubricity additives that Jet A does not, plus Jet A has things like anti-microbial additives and anti-icing additives that probably do nothing for your diesel engine. Diesel is also slightly heavier than Jet A, although I don't know the exact differences and, it has a few more BTU's per gallon. Rik, if you ran your Rabbit on Jet A that long I'd say you were probably lucky... or the thing leaked enough engine oil into the fuel to keep it going. Rabbits leaked everything into everything else! I drove my buddies Rabbit (no Jet A in this one) from Tucson to Las Vegas and literally had it floored the entire time, just trying to keep up with the heavier trucks - but not succeeding very well! We got there, which is what counts. If nothing else the thing kept running and running!
Burned lots of Jet A in small industrial boilers in lieu of No. 2 Fuel Oil circa 1982. It was cheaper because the fuel terminal operator had a take-or-pay contract and the airlines were in a slump.