I try to grease about every ten hours though I adjust the interval depending on the work being done. If I am just carrying rock or logs in the loader, I might let it go longer. If I am scooping up mud, I shorten the interval. My goal is to have 'fresh grease' on the pivots. I leave grease on the zerks and at the pivots to be a barrier from grit getting in. Tikme to re-grease, I clean the zerks and pivots, let the new grease 'seal it up'.
I'd keep my tractor cleaner but, being a machine that has a job to work the dirt, it gets filthy in a day. So it gets washed once or twice a year. I'll hit it with compressed air or a leaf blower to get the pollen or dust/grass/leaves off.
My dealer did a great job PDIing my tractor. I found nothing wrong. Glad to know your dealer cared and made things right. No one is perfect and mistakes happen. Owning up and resolving (because you are the one really paying his bills) problems is all you can reasonably expect.
I have a neighbor in the construction biz. Greases in frequently. There has to be 1/2" of play at every pivot on all his equipment. I think they use sand as a lube.....