In my line of work as a project manager, milestones are noteworthy and consequential points in the lifetime of an event or process. They are indicators of significance used to measure or mark project status. But milestones are also gauges of important life events.

Case in point, I was joyriding in my Midnight Blue 2009 Porsche Cayman one summer afternoon — windows down with the melody of the open exhaust bathing into the cockpit. I peered down through my sunglasses into the cluster of gauges just fast enough to catch 50,004 miles flip on the odometer.

I felt an immediate pang in my stomach. Not like heartburn (or worse), but the same sensation I get when I forget an important birthday or realize I left the house without my wallet. I don't like missing odometer milestones — undoubtedly a trait my father left to me.

Dad was forever calling out unique mileage readings on family outings, and I may have been the only one of six kids who understood his enthusiasm. To this day I watch for odometer uniformity — however curious the pattern. 020202 may be meaningless to you, but to me it's worth a picture.

I admit that turning 50,000 miles on my Cayman made me a bit melancholy. It's not just a number — to me it represented the midpoint of the life of my car. Like gray hair, wrinkled skin and forgetfulness, it reminded me that it wasn't so long ago I drove her home from the dealer.

And I can clearly remember the first week of possession. I watched as the mileage climbed — three, four then five hundred miles. It wasn't until I tipped 2,500 on my 52nd birthday that I noted the initial novelty had worn off. My Cayman was now as comfortable as my sneakers.

At first I fixated on the clicks of the odometer, watching as numbers ascended and leading zeros disappeared. 10,000 miles passed within a year, and much like celebrating my 25th, it marked for me the stubborn resolve of maturity.

Once I got over that hurdle, 20,000 and then 30,000 were somehow less impactful. After all, her whole life was still ahead of her — the excursions, shows and events seemed limited only by the distant horizon.

I reached the warranty period of four years well before the limit of 50,000 miles, so I should have been prepared when it announced itself that afternoon. But the distress of the numeric series displayed on my Porsche's odometer had still taken me by surprise.

Like my Cayman, I was 50-something and abruptly aware of the limitations of age. I noticed for instance that teens and 20-somethings have started holding the door for me now, and wait until I navigate the threshold as if I'd run out of fuel midstream. It wasn't so long ago that I was them.

It felt like I had jumped from 25 to 50 overnight — without warning or permission. The years and events seemed to have passed with little consequence. Aging parts and a fading appearance became more and more obvious — and I'm not all that sure if I'm referring now to my Cayman or me.

I confess I took better care of my Porsche than I ever did of myself — you would never have found crumbs or candy wrappers anywhere near it. A little attention is all my Cayman ever needed to look her best for a night on the town. I would be much less confident making that statement of my own appearance.

There's only so much we can do to slow the aging process of man or machinery. Crossing over the threshold of maturity might be easier for my Cayman than for me, its aging driver. But the sting of realization is the same either way.