Couple things:
1. A properly designed 4WD/front wheel drive assist axle should have a gear ratio and tire sized appropriately so that the front and rear wheel ground speed is as close as possible to the same. If not, this is just asking to snap drivetrain components and is a terrible design. Furthermore, if the design causes the front wheel ground speed to exceed the rear wheel ground speed, it will put all of the power to the front wheels while slipping the rears, which is not what you want considering that the front axle is typically a weaker link in the chain. So do the front wheels have a higher RPM? Yes. Do they do this to achieve the same ground speed as the bigger rear wheels that spin at a lower RPM? Also yes.
Not quite true for tractors with 4WD. For something that's going to be going down the road at 100MPH, yep, gotta be, or you will certainly cook the gear oil or the tires from heat. However, Kubota tractors, in particular the little ones, are designed so that the front wheels are trying to go 'faster' than the rear wheels. Differential gear ratio and tire size are chosen to give about a 2% lead IIRC, on the front wheels. Not just rotation because they're smaller, but they're intentionally designed so that the front wheels try to drag the back ones. Obviously this is not going to happen because the rear end of the tractor is heavier than the front end (except perhaps when there's a very heavy load in the bucket) and the back ones have a much larger footprint (traction). So why would you want the front end trying to go faster than the back end? Think about it. Going forward uphill, the front end is pawing at the ground to keep the front end pointed that way, in front. Keeping the front in front is always a good thing. Going forward downhill, the back end is dragging it's feet to keep the back end where it belongs, in the back, because the COG shifts forward (especially with a loaded bucket) giving the front tires increased traction. Even if you lose traction on the back end, you'd still have braking with 4WD because the front end is mechanically coupled to the rear in 4WD, and braking the back wheels will brake the front wheels. This is actually what gets some folks in trouble with a heavy load lifted too high. Braking with a lifted load is quite likely to put the tractor up on the front axle, at which point it will likely tilt to one side and shift all the weight to one front wheel until the pivot stops make contact with the axle housing. The result is a broken axle or a tractor laying on it's side, neither of which is an enjoyable event. On the FEL valve on the LX2610, there is a 'Float' position for the boom which is fully forward with the joystick. Forward for two reasons. 1, it's in the general direction the boom needs to go in an emergency. 2. If the tractor is in the process of tilting forward, you're going to automatically push the stick forward as you move forward in a panic reaction. This will drop the load like a stone. Better than turning over, though. NEVER, but NEVER try to back up a hill with a heavily loaded bucket lifted more than a couple inches off the ground. That will quickly test Darwin's Theory of Selectivity. As soon as possible, point the front of the tractor up the hill if you want to go up the hill.
Normal use in 4WD on soil is not going to significantly wear the tires. Turning it sharply on hard packed dry soil however is little different than doing the same on pavement. The LX will turn a LOT sharper than your turf will tolerate in 4WD, so if you're on the grass, make sure you're in 2WD unless you're creeping straight ahead. Turning sharply in 4WD generally causes a very pronounced hop on the front tire in the direction of the turn because it will try to out-run the one on the other side due to the increased speed on the rear one on the other side. I.E., if you turn left, the right rear wheel will turn faster, trying to make the left front turn faster. The left front will start chewing up whatever you're driving on or chewing the cleats off the tires, or the right front will start sliding if you're on slippery material or wet smooth pavement.
If you're spinning the rears, put it in 4WD. If you're moving material up or down slopes, put it in 4WD. If you're mowing the zoysia grass in the front yard, you've got the wrong machine, but put it in 2WD, UNLESS you have a steep grade in the front yard. Then, yes, put it in 4WD. If you're not spinning, not on a hill, on hard surface (pavement), going faster Low Range would let you go, put it in 2WD. If you need 4WD, you're better off in Low Range, too. DO NOT try to turn with the Dif Lock set. The back wheels need to be able to turn different speeds in order to change direction.
As for wear and tear on the gears, mechanical things break, eventually. Just accept that fact. How long before that happens is GENERALLY in your control based on how you operate and maintain the machine. But sometimes, bad things just happen. Defecation is happenstance.
