ok, so apparently the Legacy behaves the same as the X. I got this response to an email from Airvape Support:
"Even if you are not drawing vapor through the mouthpiece, it will stay at the desired temperature and continue to heat the herb. The AirVape Legacy will turn off after 3 minutes of use and 30 seconds without movement. Regarding the power mode feature, the Legacy does not this feature but we do appreciate your feedback on this matter and this maybe use on future product development."
The power mode remark is in response to my asking whether the button was a trigger or an on/off switch.
I don't know that I want this thing anymore. I already have a Mighty and an Airvape X if I want a session vape.