There are dealers reported in this forum trying to sell very expensive 4 year maintenance plans for the Taycan while the car needs only brake fluid and cabin air filter replacement every 2 years.
Btw the battery is covered by 8 year factory warranty.
Can't you always buy it after 4 years just before the end of the original warranty? Why buy it now? At that point you will know if you want to keep the car for that long.
You should also accept the cost of servicing a Porsche. It is probably not a big deal for the Taycan which does not need a lot of maintenance. But if you own an ICE Porsche, then it is ~$500 for the minor service (only oil change and visual inspections) and ~$2000 for the major service. Service...