Threaded fasteners. What a wonderful topic - books have been written on it. Unfortunately, I've had to read several of them! When my dealer dropped off my tractor a couple of weeks ago, he specifically said to be sure to check the wheel bolts 'periodically'. He said this was "because they were steel rims". I kind of chuckled and left that one alone; however, the conclusion was right even if the reasoning was shaky. If I had to place a wager (and I'm not), I would guess that a wheel coming off at 75 hrs, was not a factory installation problem.
Oversimplified, I'd say the three key factors in the connection are:
1. Preload - that's what the torque req't is. If this isn't done correctly, the bolt can come loose (with either too high or too low a preload).
2. Joint Stiffness - this is materials. The dealer's 'steel rim' comment could apply here. The preload specified is specific to the materials the joint was designed for. Change rims, change fasteners, the preload could be wrong.
3. Load - Unless there's a basic design flaw, vibration or impact loading are the surprises that can catch or overwhelm a joint. There is always a load at which the joint will fail (material failure or bolt loosening). In the aerospace industry we used to always loctite then safetywire every threaded connection to ensure integrity.
My recommendation would be to periodically check any bolt on the tractor that was installed as an 'add on'. These would be bolts that aren't painted. Paint is a great "loose detector" - you can just look at these bolts and see if they're moving. Wheel bolts, add on brackets for things like loaders, backhoes, mowers, etc. fit this category.
On my tractor, what jumped out at me was the nice shiny Gr. 5 bolts on the nice shiny painted white rims. I'll bet nearly every tractor is done like this but from a joint design standpoint (perhaps theoretical) this is a no-no. The joint could be relying on the paint! I'd bet 999 times out of 1000 (maybe less) the paint scrapes off during initial torqueing but the one time it doesn't . . .
I'd bet dealers all have stories of bolts loosening. I think it's prudent to make a point of looking these over, just like all the other things you're regularly checking over on any piece of mechanical equipment.