The hot wire for the radio is built into the factory wiring harness. Its not hot all of the time, its only hot when the key is turned on. Most new after market radios have a built in memory so, if you do turn off the main power, it should not loose any stored information. I have had times when I didn't use my tractor for a few months. When I did use it, I noticed that my radio never lost my clock or station settings.
Yes, the remote is a nice feature and I use mine a lot of the time. I'm looking to upgrade my speakers now. I want to add in a sub for that movie theater sound effect. Yes, it does sound funny to add all of this audio equipment to a tractor but hey, why not its fun. Being in my tractor and using it for what its intended for or, just being in it to go and get the mail it's still my way out from the daily grind.