Please also be mindful. These old devices don’t receive security patches and are going to be connected to the internet. Any exploit or bug and you’ll have a compromised device with local network access and even gps in the hands of bad guys.
There’s also the battery as OP said. It’s better if you take it out, if possible. Do not leave it running on 100% all the time or you’ll have a fire in your house!
It was late yesterday and I didn’t realize I made it sound scary! Yes to all you said! The heatsink is a great idea, too.