Hitachi ZX60 Dirty Final Drive Oil

Hi, first post on this forum after years of helpful information. I have a ZX60-USB-5N, which is essentially the same as a Deere 60G. It has 3180hrs, of which I have had it for only about 150. Great forestry cleanup machine, mostly using it for picking up slash and burning it, as well as building a road other property maintenance. I changed the final drive gear oil last week, and pulled an oil sample from each one. When draining it visibly had a lot of very fine metal particles like gear oil usually does, and I didn't see any big chunks. Since I'm an engineering nerd, I filter my oil samples through a .5 micron filter patch with solvent so I can look at any particles with the microscope. For engine or hydraulic oil i also typically pull enough of a sample to send to the fluid analysis lab, but I did not do that for the drives this time. The right drive had what in my limited experience I would call a 'normal' amount of particles on the patch. The left drive sample fully clogged two patches, and was totally coated. The particles are so dense and small on the patch that it is hard to tell much about them, but I believe they are mostly metallic. I probably need a higher magnification than my cheap pocket microscope has. Filter patches: (the pattern on R Drive is from the glass filter support. Particles mostly collect over the holes where the fluid is sucked through) Microscope Photo: I did note that the drive fluid plug hex was pretty stripped, and they were almost impossible to get out, so it is possible they missed the last service interval on the L side. I am considering doing another fluid change after maybe 10-50 hrs and see how things are doing. It's only about a quart of oil per side. Other than that, is there anything I should consider? Should I run it until performance suffers, then investigate / rebuild / replace? Would appreciate any advice! I'd love the machine to keep running until next winter just like everyone does....