To minimize tire wear, air up all the tires to the max bead-seating pressure indicated on the sidewalls. Tire wear is caused by the tread area "slipping" as the tread flattens out and curves as the loaded contact patch rotates around the tire. If the tire is inflated to max-pressure, that contact patch squirm - and tire wear - is vastly reduced. Both fronts and rears. Air down for work.
I terms of varying engine speed, the theory is that as the pistons go up and down bores, the wear on the piston skirt against the bore happens at different areas of the bore at different speeds. So vary the speed, 1900 rpm ~ rated speed (2450 rpm?). Every power pole along the way, throttle up or down a couple hundred rpm.
If you are concerned about front diff bearings and seals, or rear axle bearings and seals, get some sort of work wagon (inexpensive wheel bearings) and put the 3-pt implement(s), and maybe even the loader bucket on the wagon.
My biggest concern of 3~4 hours of on-road time would be the car-driving people in hell-bent hurry to get somewhere and crash into you and/or each other. There are usb-rechargeable magnetic orange-flash "beacon lights" that you could charge-up and stick to the top of your ROPS frame. Check your local laws regarding use of such lights, but generally, more warning lights will reduce your odds of being part of a wreck.