There are 4948 pages of campaigns. They are sorted by last updated
EDIT: Read farther along the thread, mistakes were made and corrected. /grin.
Page 4948 has campaigns that haven't been updated since 2007.
Starting at page 1 (updated within hours or minutes) you can go back to page 10, where from that point to 4948, all the campaigns are at least a year since an update.
That leaves 4938 pages of over a year since update.
This does not mean they aren't being used, (although I wager most are not) just that they haven't been update in over a year.
edit: there are 12 campaigns per page, meaning roughly 59,376 campaigns, with 120 updated within a year.
I might comb through the first 10 pages and count systems in a day or two.