If you use an extension, make sure it is fully uncoiled. If you need to coil it, do so in a figure of 8 which prevents it from overheating.
I use mine once a week after a charge up to 90% at a fast charger (it goes down from about 50kW/h at 80% to 35kW/h at 90%). Trickle it up to 100% from...