I had to oversee several major maintenance inspections as an Executive Officer in a Battery as well as Pre/Post deployment maintenance inspections in an motorized Infantry unit aside from the monthly/weekly time at the motorpool/gun park.
My experience was that the unit that is about to deploy is fixed up, meanwhile the rest of the units are just hovering at about 50-70% deadlined and in a state of swapping gear within the Battalion just to support training/field op cycle.
For those who've not served. Consider that in units with lots of equipment (tanks/Artillery ect...) maintenance is about 1/2 or more of your man hour work load for a combat arms unit ( even more focused for aircraft) you still have to conduct PT, conduct field ops (a week or so at a time) do annual training and "safety stand downs" administrative work ect... plus there are professional military education events you send your Marines to which also takes up your small unit leaders and supervisor's time.
Further more the operation tempo (at least as I experienced it in the Fleet as an Arty Officer) is insane. Frequently you also had people fudging maintenance reports and wasting Tax Payer dollars as Easy C said.
No-one wants to admit that the military's readiness is completely in the tank from a result of 2 decades of endless war. Its the proverbial "self licking ice cream cone" as no one wants to admit that they are combat ineffective therefore they find ways to cut corners so that they dont have to put a bad report up to higher.
I got myself into some trouble when I reported the actual state of not-being-ready of our gear at one point. Got my battalion commander (my boss's boss) in a lot of hot water for pointing out how bad we actually were in relation to the table of organization and equipment standards. This ultimately resulted in me being moved out of the battalion and into a new unit after I had already identified all the problems, and solutions for fixing the unit up pre-deployment. Thankfully this would up resulting in a positive outcome as I went on the deployment with a different unit in a different role, and had much more positive effect on my career.
I grew up close to one of the largest AF bases in the United States. And there was a very sad incident where I believe an E-7 sergeant had signed off on the maintenance of a fighter jet. This was a brand new plane and when the pilot went supersonic, it just disintegrated. The sergeant was viewed as the culprit responsible, and when security police showed up at his home to retrieve him, he knew what was up, and he went to the backyard, where he had built his son a tree house. The sergeant climbed into it, took out a handgun and ended his own life!
Later, an investigation found that the sergeant was not responsible in the sense that what he was required to do for maintenance would not have detected the defect in the plane. It was in fact a worker at the factory who had done something very wrong during the assembly, which created a hidden "ticking time bomb" for any pilot.
I remember how the sergeant looked just like a real life Ned Flanders, a character from The Simpsons. If only he had not given into his fear and self-doubt...