On one side, you want to recoup the miner investment and run it as much as possible, ideally 24/7. But on the other side, you want the heater to regulate tempe

On one side, you want to recoup the miner investment and run it as much as possible, ideally 24/7. But on the other side, you want the heater to regulate temperature (not overheat the room) by switching itself off as needed. You can have both only if you either waste energy (vent it to outside) or have a thermal storage. It is already existing technology i.e. for electric heaters that accumulate heat using cheap night electricity and slowly release it during the day. Or water boilers. But they are bulky and can only store several hours worth of heat.