Outbound and others - thanks for the thoughts. I just completed a couple week long winter trip, running the heater fairly continuously. I have tried changing the runtime in the menu - just to see if changing it to a reduced time (versus infinite) would make a difference. It did not. About 8 hours in to the 12 hour test (720 minutes is the longest I can set) it shut off with the 'no signal' error on the easystart timer.
On my most recent trip, the heater ran a lot. Parked at ski locations and basically kept it running continuously (as much as possible, between 'No Signal' errors) except when we were driving to a new destination. On a few nights the heater ran all night through, but most nights it would quit sometime in the small hours of the morning - timing isn't really regular, sometimes 5 or 6 hours, sometimes 10 or 12 hours or more. But the error persisted so much so that I got in the habit of listening for the pump/fan running anytime I would wake up and roll over. And we installed a switch next to the controller to cycle the power off and back on again so the 'hard' reset of the easystart timer is now easier than previously pulling the fuse. But annoyingly the problem persists despite rewiring multiple ways, replacing the factory connector with hardwired connections, multiple trips through all the menus, and several discussions with tech support at heatso.com. No faults reading either (even when the controller is directly connected to the blue/white wire - bypassing the altitude kit)
My big question now is... what do I replace? The easystart timer controller? the ECU on the heater? Something else? I don't want to start spending money replacing things and replace the wrong thing. Maybe the solution is to replace the entire thing and get a Webasto?
Anyway, its frustrating. As usual, any suggestions that people have is welcome. And thanks again to those that have offered insight previously.