FWIW, I have 82 INSTEON devices
I have followed best practices here for sending multiple commands (1-2s delay as appropriate). I don't have a ton of triggers on the devices that send other INSTEON commands, at least not relative to the number of devices.
In my case 1 to 2 s delay from signal to action is way too much. One of my examples: I have three setts of 4 kypadlinks that have most of the lights in the house and some scenes programmed to the buttons.. I want them to be in sync. So If I turn on a scene with sevenlights (one of my living areas, mood to 30% for most) one button sends a scene request to the lights. This triggers 7x4 button updates or 7 scene updates with with 4 modules in each to the buttons (I tried various ways). 28 insteon commands, or 7 scene commands (they were separate since turning any of the 7 had to be individually changed as well). From my perspective, (even more so from my wife's) this is a perfectly simple function. But.... What happens, is that the scene command generates 7 scene cleanup commands, 28 keypadlink commands for a total of 35. Now, If I space out the 28 keypad links by 2 sec, I get a minute delay until all the buttons sync. Now even worse, and quite common thing is that she decides that actually she doesn't want to turn them on so presses off after a second or so. Now, the lights don't react, so she presses it again, then again and calls me with a an annoying voice that the lights are broken again. And I can't do anything now for couple minutes because there are insteon messages running around and bumping in to each other. Even without the delays, but with clean up turned on, this was happening very often. Even worse with guests who expect the lights to go on or off when they press the button, And if they don't in a second or two, press it again and again and again. This is all happening while people are moving about the house triggering motion and door sensors, that turn lights on an off.
My solution is to remove all the keypad links, turn off clean up and just send two consecutive scene requests to the lights. And yes it works well. But I really liked the idea of the keypadlinks.
Interestingly, I could detect INSTEON communication via our baby monitor whenever my son was little -- it would show interference any time a switch was hit and you could tell the length of cleanup and "bouncing commands" until it settled down. It did seem excessive for what it was doing (e.g. turning off a light without any triggers). We had one device that must have been bad or had a band link or something as it would generate about 1 full minute of communication any time it was tapped. That doesn't seem very prudent from a reliability standpoint.
1 full minute of communication for a single switch is excessive.
I have no reason to move off INSTEON devices, but I do have all sensors and other quick-transmitting devices on Z-Wave
I plan to leave the insteon switches for lights only, and change most everything else to z-wave. From reading around, this seems to work well for people.
To me this means that making a complete Insteon automation system with sensors, switches and extended logic for a large system is difficult to impossible. I suspect that If all the sensing is done with z-wave and insteon only handles turning on/off switches I should have no issues.