Only 11 days late, better late than never though. My case for not wanting Who's Online to be set for 30 minutes.
Let's say I come to visit the MB, I see which threads have new posts, I look at them, and I leave. For 30 minutes, new posts are being made, and the MB thinks I'm here, but I'm not. At 30 minutes, all posts that currently exist, including tons I've never seen, are marked as old. When I come back later, there are tons of posts (30 minutes worth) I've never read, but the MB thinks I have. Is this how it works? I believe so. I may be mistaken. What I EXPECT to happen is that the MB should've recognized I was gone in 15 minutes or whatever, and started remembering the new posts since that point.
I have sometimes had the MB say I was idle to long and mark all posts as read before I read them, if I had a long post to type. So I read short threads first. If I'm in EoEO typing up something huge, I JUST LOOKED at the forum list, so I still have a vague idea of what's new and what isn't. On the other hand, with the scenario above, I have NO IDEA what's new and what isn't, because I haven't been here for a long time.
The whole point of Who's Online is to show who's online. If you're gone for 30 minutes, you aren't online. I used to look in Who's Online to see who was here so I could PM them and maybe get a response immediately. Now I have to go to look at everyone's activity, and watch them for 5 minutes and see if they're shown as looking at the same page all that time, and if so, they're probably gone but the MB thinks they aren't. Who's Online no longer serves the purpose of showing who's online. I had that problem in the past too with the 15 minutes, but nowhere near to this extent.
This is aside from the fact that our online members list is showing hundreds of members as being active at any given time, which is never true.