So we're running out of topics to discuss, and have resorted to talking about what we talk about
I usually skim the first page, if it spills over to 2-3 I would read through the longer posts, before posting, If it's already 5+ pages I usually don't bother adding my 2p.
If it's something I've already posted on I would find my previous posts and try to read the ones after to see if they're relevant, but agree with the above when you make what you consider a killer point, and noone responds it is frustrating, especially when you then see a very similar point made in a couple of pages time.