1. The leak sensors send a heartbeat status about every 24 hours, give or take.  Why you often see a "wait 25h" is to allow for a little fudge on that.

2. Yes, they should stay running.   They are started at ISY boot, and they wait for a heartbeat trigger.   Then they wait for about 24 hours for a program retrigger.   If it arrives, the ISY restarts the program, for a new 24 hour cycle.   If the heartbeat doesn't arrive, the wait falls through, and the notifications start (until the heartbeats start arriving again).

3. There's no "exit" on these programs, at least explicitly.   Are you aware that, if a condition in a program IF changes while a "wait" command is waiting, that the wait is aborted and the program restarts with the condition getting re-evaluated?   If not, that may be an important clue to understanding how much of it works.

Thanks for the heads up about the re-evaluation of the variable from the wait state.  That clears up a mystery for me.

As to the other questions, a system reboot got everything straightened out.  I did receive a random "Leak repaired" e-mail, which was NOT preceded by a "Leak Detected" message which I can't explain. Status of the sensors on the main page was OK, but one of the variables did not reflect that status. I guess I don't understand how they can be different.  Everything has been OK over the next 25+ hours.   

This event driven programming is new to me, although I'm familiar with several other languages.