Logo text This column contains spoilers for the May 10 series finale of The Comeback , though is The Comeback really the sort of plot-rich show that you worry about having spoiled for you? A good finale — a good planned finale, at least — is the destination of a journey measured in years, in seasons, in episodes. HBO’s The Comeback is a uniquely modern show insofar as Sunday’s finale was the culmination of nearly 21 years since the series’ June 5, 2005, launch. Or maybe it was the culmination of three seasons — pretty reasonable by today’s premium cable standards, but hardly epic. Or perhaps it was the culmination of 29 episodes of television, roughly the number that The Comeback star Lisa Kudrow ‘s Friends would produce in its typical season, plus a month.…