My battery warranty from tesla expires this october. I signed up for a 2 year warranty via 057 tech (frequent poster here)
The regular used warranty, unless it was a Tesla CPO that the previous owner bought before they removed the free supercharging, is long gone. I don't think you could have extended the warranty on the CPO warranty (whichbwas already an extended warranty on its own). I had several things fixed for free with that from October until it expired in January.