And to add my two cents:
I worry that dividing the threads up regionally would mean DC info gets spread across different threads. So many of us bike from VA or MD to DC, and it would be natural to just post one story of your commute. I don’t mind having to read the (little bit) about Maryland, if it means I get more good intel about DC.
I do think that when the trails are (mostly) clear, it makes sense to “reset” and start a new thread. For example, there are 19 pages in the January thread, mostly about last week. This weekend’s temps cleared a lot of the trails and roads, and this week is going to screw them up again, so it would be nice to start on page one. In the winter months (because summer is just not that active), maybe we divide the months up into thirds? or weeks? or maybe weather events? Weeks is probably the easiest, with the week starting on Sunday, meaning the current “January 2015 Trail Conditions” thread should be “January 4-10, 2015 Conditions” and now we should be on “January 11-17 2015 Conditions” (I think we should drop “trail” because people talk about roads and trails just the same).