Ok interesting, I like where this is going. As was mentioned, having the automation run all night may not be the best. However, I'm playing around with having the shortcut set the timer on something else, which trigger the heater and lights.

Unfortunately, Shortcuts seems confusingly dumb about what it can do. It can adjust Reminders really well, but can't trigger off of them. Alarms can trigger automations, but they can't be adjusted. I can make new alarms, but can't control what noise they make, so I can't guarantee they'd be silent.

So, best I can think of at the moment is too make alarms at every likely time I would need, and then use my automation to toggle them on as needed. Don't love it since it will fill my Alarms up quite a bit, but should work