I would seriously consider the tethered option. You say you will charge every 10 days, but that is using the old ICE fill up thinking. If you switch onto an EV tariff, you will get around 4/5 hours of charging, this may not give you a full charge in one go. With the the tethered one, I plug in almost every day, takes around 10 seconds to plug in/unplug each day. You know it is fully charged for when you need it. When it is raining, is a pain to deal with removing a non-tethered cable. Just give it a thought before you commit.