Aircraft have a designated point - expressed in operating hours - at which certain major components should be evaluated for possible overhaul or replacement. This recommended duration is referred to as TBO: Time Between Overhaul. A simple piston engine on a light airplane, for example, might have a TBO of something like 2,000 flight hours. At the other end of the spectrum, there are parts on the Space Shuttle main engines with a TBO expressed in flight minutes. The complexity of the component and its critical role in safety both factor into determining a recommended TBO.Generally speaking, our bodies don't come with a TBO. Sure, you might need a few teeth filled or capped, something expendable like an appendix removed, or a vein from your leg used to bypass an unhealthy blood vessel in your heart... but typically the
stuff you're born with is the stuff you die with. I think that's why I'm having a hard time getting my mind around the concept of actually getting a new part. They're taking something out and putting a new one in. My left hip, for all practical purposes, has reached the end of its useful service life. I guess it's at TBO.I don't know about you, but I don't spend much time thinking about the machines that are our bodies. I don't think about the electrical impulses that fire the chambers of my heart in a specific sequence, which is good because I have a hard time getting an entire string of Christmas lights to illuminate when I take them out of the box. I don't give a lot of thought to the arteries that carry oxygenated blood to every cell in my body nor the veins that bring the blood back to my lungs... probably because I can't get my backyard sprinkler to stop leaking, no matter what size washers I use nor how tight I twist the fittings. There's just a lot about the human body that must be taken on faith. For most of my life, I've bought into that concept just fine. Some things are just too huge to ponder.
My neat little paradigm is being shaken as I approach surgery date: One part is being taken out - and a new one is being put in its place. Suddenly I'm thinking of my body as a series of components rather than just "me." It's a little scary, truthfully, but it's also a great time to ponder the wonder of our bodies and their many systems. How incredibly fascinating that biomechanical engineers are still working to perfect such a simple thing as a prosthetic hip - a ball and a socket - when most of us are born with two perfectly-formed and functioning models without anyone giving it a moment's thought.
But the TBO model is flawed when you're on the fence like I was for a few months - trying to decide whether or not to go ahead with surgery. I'd wished for some sort of objective criteria, like the manual that comes with an airplane engine, something that said, "Yes, this is the time to get it done." Some people say to wait as long as you possibly can - these replacements, they caution, might not last forever. For me, it came down to a quality-of-life now decision. There's no guarantee any of us will get those "golden years" anyway - so why put something off just because you might someday need a subsequent procedure (a "revision" surgery). TBOs, at least for the kinds of airplanes I've flown, are recommendations. The mechanic, pilot, owner, maintenance supervisor - someone - takes a look at the part, measures the wear and tear against its expected life, looks at the part's critical role in flight safety, and considers the recommended TBO - before making a human decision. Do we replace/repair now - or do we push it a little longer?
There's no TBO on happiness, on quality of life. There's nothing I can measure with a micrometer, no test I can do. It's my decision and I've made it. The time to live is now. That's why I'm going for it.
