Peter -- I get it. Man, do I get it.
I'm not sure whether this will help or not; but I've owned the red 280SL for 22 yrs now and intend to keep it forever. I've loved the W113 since I was a kid, and IMHO some things just get better with age; such as good art & architecture, some red wines, and certain cars. The W113 seems to have the unusual ability to stay reasonably current with relative ease. As a comparative example, my next door neighbor has a lovely little MG TF. Pretty little thing. But I wouldn't be interested in driving it or riding in it for any length of time. On the other hand, my wife (who is particular in the extreme when it comes to comfort) recently declared the 280SL to be as comfortable as our CLK cabriolet on long driving trips. And to us the 280SL is simply more interesting, more entertaining, and more fun as a driver than a newer or even a higher-performance car.
Personally, I don't care much for any depreciating asset. But I have punched the calculator a lot, and figure in the long run (meaning decades) that by keeping the 280SL at the level of a "new car" it will actually cost less than buying another new (expensive) car every few years. More fun, more interesting, and at a little less cost...with the hope that some day we W113 owners might actually see the values of our cars markedly increase. Again, not that I ever intend to sell; I just happen to enjoy assets that appreciate more than those that don't. Just one man's view perhaps...
Tom in Boise
'71 280SL 4-spd, signal red w/lt. tan interior, restored/enhanced