While I am not a commercial lawn/landscaper guy, I DO cut and maintain my own large acreage of about 6 acres to be cut. I was wondering if some multi-contract commercial folks would chime in on their maintenance schedule that they follow for their mowers. I think it would be helpful if the pros would share what they've learned from experience and what works for them. At the top of my personal curiosity is if you perform your own work or use your dealer's service department and why? How often is the engine's valve lash checked/adjusted? Oil/filter change intervals in hours? Greasing the front spindles and other pivot points that have zerks? Hydraulic motor fluid/filter change in hours? Anything you do to add longevity to your machines such as changing certain parts BEFORE they cause breakdowns? Is it not important for commercial pros to keep their equipment in good working condition to avoid downtime and downtime is income lost? Even though I am not in the business, I have experienced a sudden breakdown while cutting a distance from my house and tools and then had to lug tools and parts to the mower in the field to make repairs. That's when I decided to not wait until consumable parts would fail and cause the same miserable situation. Lesson learned. Now, I change certain parts before they can fail and that has turned out to be valuable. I use the owner's manual as general guideline but some maintenance chores are done more often than recommended. Engine oil/filter is changed much more often. What do you do and why?