You're going to have to rig up a pretty effective forced air cooling system to attain safe ground runs any longer that 15-20 mins
I wouldnt run jab any longer than 15 on the ground, so it would take 200 cycles of 15 minute runs and 20+ minute cool downs to get the 50 hours.
shorten the cool down times and you wont make the next 25 minute run without cooking something
I dont consider that a practical operation, I suppose it depends on how much free time you have