I actually just searched for this thread to see if there was something on this topic, so I wanted to chime in as to what part of its purpose may be. I think these discussions can be helpful for those of us who do not live in New York and who may not know much (or anything) about how these things work and why decisions are made. Through these boards, I've learned about running costs, recouping, theaters kicking shows out, and how things like awards/nominations/licensing and touring potential may affect how long producers keep shows open. For me, even though of course no one can predict anything with certainty, this information helps me plan my trips to best optimize my chances of seeing everything I want to see. It didn't used to matter when I got to New York only once a year or so because I'd just see the shows at the top of my list, but now that I have a lot more opportunities (but still not unlimited options), and can go deeper on my list it really helps me organize my trips. After all, I can't just wait for a show to post a closing notice and know for sure I can go snag a ticket if I won't be back for several months.
For example, I sought out this thread on bright star because I am coming to New York with my parents in June, and I will be there with other friends and on my own a few times between now and then. I really want to make sure I see this show, but I would like to see it with my dad (who loves bluegrass) in June if possible. So if I think there is a good chance it will stay open, I'll wait. Fortunately for me, with two trips in April and one in May, I can wait it out a bit more before deciding in this particular case, but sometimes that's not true. So if I'm planning a trip and know I'm unlikely to be back for a few months, it's helpful for me to know which shows I want to see are most likely to close before a return visit. I don't think it's a negative thing, particularly since most of the time when I read these threads most people are not celebrating the fact that a show isn't doing well at the box office but are saying it's too bad shows they enjoyed didn't do better. (Of course that's not always the case, but it doesn't take long to figure out whose comments are more helpful/informed than others.)
So thanks to everyone who provides their thoughts and information. It has actually helped my planning tremendously and I've been able/will be able to see nearly all the shows on my list this season!!