What does lastheardfrom and online do for unplugged Insteon devices

Version 3.3.0.M6 and prior versions on Windows 10 with Insteon Hub II

I have several Insteon micro switches and outdoor on/off switches connected to devices that are generally not plugged in until they are used…

I’m getting LastHeardFrom change updates for these devices when they have been un plugged for over a month.

Am I doing something wrong ?

Is this expected behavior ?

It seems to me once unplugged a device would no longer have updates in the log every few minutes and become offline in the things page.

Thanx for any thoughts on this.