Arguably, the conditions under which these events happen should be a
bit different, but the rules are complex enough here that I've tried
to have this commit be pure refactoring.
Closes ticket 25952.
Finally, before this code goes away, take a moment to look at the
amazing way that we used to try to have an event happen
every N seconds:
get_uptime() / N != (get_uptime()+seconds_elapsed) / N
Truly, it is a thing of wonder. I'm glad we didn't start using this
pattern everywhere else.
