Someone just templated this onto the page: "The organization of examples below assumes that the page will only ever be read in the middle 2000s, when it was written. From the vantage point of 2020 most of the headings, while technically true, are also outdated. They need to be changed to indicate the decade in which the work originated, not how long ago that was in 2005."
Unfortunately, if such a change were to be made, it would require the article be split into two separate lists - one for series which are still running (ordered by start date), and the other for series which have concluded (ordered by run length). We know how many years of Guiding Light will ever exist if the last episode was shot in 2009 (72 years) but Sesame Street? 10 Nov 1969 and still going strong.
Anything listed as "still running" will likely have to be rechecked in any case, as some of these series have wrapped up since this was written.