if you are going to have a problem, chances are it wont be related to your maintenance intervals. a lot of it is the luck of the draw. i have never heard of anyone's engine going because the oil was too old. you have trouble when you use the wrong oil, have no oil in the engine at all, plugged radiator, no coolant in the engine; oil pump or water pump failure, oil plug fall out, oil filter come off, forget to change water to antifreeze for the winter, etc...
same with trannys, its never an oil problem. its either an idiot driving, a linkage problem, o ring or some small failure that leads to a big failure.
we had 2 trannys go in 2 tractors and both of them were just out of warranty and only had about 1000 hours on them.
we had one engine go once because it had no oil in it, another engine problem because there was no coolant in it.
we got another tractor with 10,000 hours on it and literally have done almost no maintenance on it since it was new. change the engine oil every 500 hours or so, throw a new hydraulic filter on every few thousand hours, thats it. coolant and transmission and hydraulic fluid have never been changed. granted, we have to add some every so often...
seems to me no one really uses their equipment these days. im impressed with the mining industry. when your running your machine over 50,000 hours and a new one cost a few million dollars, and your running 24-7-365, and losing big $$ when its down, then i would be more concerned about maintenance.
i dont have time to figure the cost of maintenence on the big tractor, but i suspect over 10,000 hours you would be well over 20k if you followed the recommendations. you could fix an engine or tranny for a lot less, but chances are you might not have a problem anyway, the key would be to put her up for auction around 8000 hours. i have quite the strategy, i know, but it works out for me.
on our skid steer, most of the pins and bushings are original with 10k hours, they just get a little loose thats all. it works good for cleaning up the uneven concrete, cuz the bucket follows the uneven terrain. sounds like im 4k ahead of the game here, since we never had a problem with it.
however, on the manure spreader, i grease the auger bushings religiously (every 5 hours or less). because if i dont, i will be replacing them instantly. i never grease the rest of the spreader, but i make sure to get those 4 bushings.