@Matt et al.: re. my leak sensor issue, I have since removed a lot of triggers for things I decided I did not need, and since then it seems that I have had few—I think 0—heartbeat timer timeouts. So it's as if the heartbeats were getting lost/missed/dropped. This is on a 2018 Mac Mini w/ 32GB of RAM running only Indigo, Simon, TeamViewer Host, and a DDNS client.
@Midnightson: I believe you should be able to "turn off" a leak sensor after it "fires"—I do all the time—except that the contacts must be dry otherwise it simply fires again. It sound like you might have a communication issue. The leak sensors can only use RF. I have added some Insteon Range Extenders (https://www.insteon.com/range-extender) in strategic places around my house, and that seemed to help with missed transmissions. Re. the battery, you could set up a "heartbeat" timer and triggers for each leak sensor, or install the Cynical Behaviors plugin (http://www.cynic.org/indigo/plugins/online/behaviors.html) which appears to provide heartbeat capability "out of the box" for leak sensors. BTW—glad to hear about the valve—I'm about to install the same on my house.