Interesting assessment, butI can only assume if we weren't meant to drive around with seat heaters on, Alfa would just tell us not to do it, and make all the levels shut off automatically at some point, rather than just the minimum. My MY19 owner's manual says, "The “minimum” setting is automatically deactivated once a certain period of time has elapsed. This varies on a case-by-case basis, in accordance with the specific operating conditions.
Note: The heated seat function can only be activated in temperatures below 39°F (4°C)."
Further, besides not telling us not to drive around with the heaters on, the manual warns sensitivity impaired people to exercise caution when using them, even on low, for extended periods. Again, from the MY19 manual:
"Persons who are unable to feel pain to the skin because of advanced age, chronic illness, diabetes, spinal cord injury, medication, alcohol use, exhaustion or other physical condition must exercise care when using the seat heater. It may cause burns even at low temperatures, especially if used for long periods of time."
My takeaway from all that is to run the heaters as you please, but don't pass out drunk with the car running, the passanger seat heater on high, and your face on the passenger seat.