A subtle change has been happening with our friend Sherlock in this new millennium. It was probably overdue, because as the saying goes, "No one lives forever." Not vampires, not Highlanders, and certainly not professional detectives.
Sherlock has successfully moved into the modern day with his TV iterations, and with those, has become a contemporary man in much of the public consciousness, just as he was when he was created in Victorian times.
Like King Arthur, Robin Hood, and the Three Musketeers, it seemed like Sherlock Holmes was going to be forever stuck in that period, early on due to a nostalgia for those times, later almost as if writers weren't as good at making deductions from modern details. In any case, when his birthday was celebrated each year, mention was made of how he was still alive at one hundred, one hundred and one, one hundred and two, etc. . . . because humans do sometimes live that long. And as that number crept up, perhaps some special bee-related diet was needed, but Victorian Sherlock living to one hundred and twenty did not seem impossible.
Now that the Sherlock of the original story would have turned one hundred and sixty two years of age, we don't hear such talk all that much. Sherlock Holmes was a man firmly grounded in science and reality: "No ghosts need apply." And neither do all the other sorts of supernatural immortals. Making him one of those would betray his entire life's work.
Should Sherlock have remained completely Victorian and has us accept that he quietly passed away at some point in the last hundred years? Or should we just allow that the legend lives on, and that an incarnation of that legend can live at any time now, to inspire, to exemplify, to teach, and to entertain?
I don't know about you, but it sure feels to me like we need Sherlock Holmes's clear observations and logical conclusions these days . . . and in a younger, vital form than a 162-year-old mummy of a man. So having Sherlock Holmes be born, age, die . . . and then be born in another era to wander that era anew as an excellent specimen of mortal man . . . well, that's just fine.
Being an immortally respawning mortal, with the chance to view each new version of our world with fresh, non-jaded eyes actually suits Mr. Sherlock Holmes better than the alternative.
He's just going to have a lot more criminal history to read up on, every next time.