Comment 4 for bug 300634

I think part of the problem is that we're not updating things in a sane order.

Consider this snapshot of the bug watches that need updating for debbugs and gnome bugs, taken at 16:50 UTC using the query at https://pastebin.canonical.com/11566/:

 * debbugs
 -- Total watches: 8728
 -- Watches needing update: 2072
 -- Watches never checked: 232
 * gnome-bugs
 -- Total watches: 9746
 -- Watches needing update: 2418
 -- Watches never checked: 390

Versus this one, taken at ~1800UTC

 * debbugs
 -- Total watches: 8732
 -- Watches needing update: 2078
 -- Watches never checked: 236
 * gnome-bugs
 -- Total watches: 9748
 -- Watches needing update: 2299
 -- Watches never checked: 391

So, unchecked watches are being checked, but there's still a lot of them and considering that we check up to 100 watches every ten minutes there should surely be less (or none) of them over an hour after the initial sample was taken.

ISTM that we're selecting the bug watches to be updated in a haphazard fashion rather than updating the never checked ones first, followed by the oldest ones (though we then have the problem of dealing with bug watches that haven't changed for months, which is the subject of bug 302529). If we start doing this it should clear out the backlog and may fix the issue about which this bug was originally filed.