1)Inspect and clean/replace the case drain filters each season. Debris will alert you to other problems looming, or set your mind at ease if there isn't any.
2) Drain the chaincase annually. I drill and tap a hole in the front bottom of all my machines so that all one has to do is "pull the plug".
3)Change the hyd filter annually, and change the hyd oil frequently--we change it annually also, but I know many people don't (we have never had a hyd/hydro failure, so I think an annual change certainly has paid dividends for us)
4) We change the coolant every other year--again, many people don't.
5) If turbo'ed, check the turbo and exhaust manifold bolts. We have had them work loose.
6) "Open 'em up and clean 'em out"--tip the cab/rollcage back and clean out the dried mud, sand, sticks, etc that will accumulate way down under everything. We blow out and then CAREFULLY wash it out. I have found that spraying with "gunk" or something similar allows you to clean everything up with a lot less water pressure. Remove the side panels that allow access to the hydros for better access if needed.
7) Check the fan gearbox lube level. We have had to "speedy sleeve" a couple of our machines where the shaft comes out of the gearbox.
8) Check the hoses for rubbing/wear. Power bobtach hoses especially.
9) Check the main drive belt and idler--we have had idlers fail in as little as 500 hrs.
10) Blow out the alternator occasionally--I've seen them jammed full of dust and debris.
11) KEEP THE ENGINE AIR FILTER CLEAN, CHANGE THE ENGINE OIL OFTEN.
I'm sure I am forgetting a few things, but this may help you some. We put a MINIMUM of 500 hrs on each machine annually--some machines a LOT more--maybe with less hours you wouldn't need to do some of this annually like we do.
Tracked machines: change the drive motor oil on each side. If you have the idlers and rollers that have an allen plug in them, remove the rollers/idlers and drain and refill them. Adjust the track tension often. I am a firm believer of taking machines in for an annual inspection each winter. It is quite cheap if you don't let the dealership fix what they find, and bring the machine back home and fix what they found yourself. This pays GREAT dividends to us.
If a controller machine, the dealer will update the software and get a list of all codes the machine has thrown, which is valuable, and you can't do it yourself. We usually allow the dealership to do a few minor adjustments and fix something we don't want to tackle, and it runs about $200-$400 per machine on average--money well spent.
We also touch up all scratches in the paint, sometimes repaint the tailgate if faded/scratched up, replace our business name/logo decals if needed, and make the machines look SHARP for another season. Other than filters, we don't carry many spare parts. We used to keep drive belts on hand, but now we just replace them when they show excessive cracking/wear, and they never break.
Hard to grease a machine TOO much, especially the pins at the bobtach.