Beginning its sixth year means that it has run about 4 1/2 years of actual performances. Thinking in terms of 8 performances a week for about 235 or so weeks, it would be closing in on 1,900 performances, which has not been achieved by a play since the mid-to-late 1940s, when Life With Father closed (unless I am forgetting something). (I am ignoring the 1 vs 2 performance requirement to actually see the play...the curtain has risen almost 1,900 times).
Say what you will about JK Rowling, but her track record is mind-boggling. The actual play would not exist had she not written the books. Personally, I was bored pretty much non-stop and got most of my fun watching a constant run of parents with little children leaving the first 10 rows of the orchestra for potty breaks throughout the show. I wonder how many of the kids who saw the show actually liked it as much as their parents wanted them to, given how much they paid fr the tickets.
One other memory from the performance I attended a couple of years ago was that Stephen Spinella played Lord Voldemort; I remember thinking how sad it was that such a fine actor had to take that job (it wasn't much of a role), but then thinking that he probably would have a steady income for as long as he wanted it, since I have never seen him in many movies or TV shows to supplement his stage income.