I don't remember when it was, exactly, that I lost interest in Superman. There was a time, from Crisis on Infinite Earths until well into the 2Ks, that I had complete collections of every Superman title published (Superman, Action Comics, Adventures of Superman, Man of Steel, etc.). I do know that I stopped buying Action Comics with #900, four issues before the title itself came to an end. There was a time, in 1986, when DC Comics wanted a new "Superman #1." But rather than cancelling the original series outright, they changed the title to Adventures of Superman with #424. Action Comics continued at that time with #584.
Then, in 2011, DC decided they wanted to revamp their entire line, including Action Comics. #904 was to be the last issue of the original run, but I decided to stop with an even 900. I say I "stopped," but actually I did continue to buy Action Comics and Superman for almost two years into the "New 52" era, but I was no longer interested in maintaining a set of sequentially numbered issues if DC itself wasn't. Except for those four issues of Action Comics, my "complete" run of Superman titles continued for some months to come. Action Comics continues, numbered in the 1000s today, but try finding issues #905-956.
I know that I didn't bother buying Adventures of Superman when it returned (with a new #1) in 2013. I didn't buy an issue until #16, which featured multiple versions of Superman. I also happened to buy #17 because it featured a story by Jerry Ordway and Steve Rude, but that was it... for both me and the series as that was its final issue.
At that time, Captain comics was doing "Cancelled Comics Cavalcade," a post-mortem on all cancelled series. As much as fans complained about the redesign of Superman's costume (sans red trunks), Cap pointed out that the the then-recently-cancelled Adventures of Superman series featured the classic version and nobody bought it. I didn't even know it! and by that time it was too late. Last week, the Superman Red & Blue series, a favorite of mine, came to an end with its sixth issue. I really enjoyed those out-of-continuity tales, so now I'm contemplating buying Adventures of Superman (2013) #1-15 in hope of reading more of the same.