Funny, informative, and more than little worrying. Thank you.
The last time I bought a car (12 years ago) I got 4 years service thrown in. How much are the routine services?
Since no one owns one, there is no exact answer yet. Based on a Cayman, and just reading what others say in the P-car online communities, I would plan on $350 - $400 for an oil change, $200 every two years for bleeding the brakes, $800 - $1K for minor service (including oil, brake bleeds), maybe up to $1.5K for major service. Mostly guesses. Then add the cost of tires, including shipping, installation, taxes, figure $1K for the rears every 15K miles. Maybe $800 for the fronts every 25K? Depends upon how you drive.
Can and do Porsche invalidate the warranty (in the US) if non-Porsche-approved mechanics perform work?
I don't think they can do that. If you have proof the work was done as required in your warranty book, you should be fine. Google the Magnuson-Moss Warranty act. It might be part of that law.
The need for a battery-tender is a shock. That wouldn't have surprised me in a Jaguar of the seventies, but a Porsche in the 21-teens?
Times change. There are many electronics always running and despite the addition of AGM batteries, the fact is there are many cases of batteries dying. Google the pcar forums and you will find lots of threads. Those electronics are always running. Two big problems with the AGM batteries seems to be heat. Heat not good for them. And, leaving the car unlocked seems to really be a drag, but that could be because the sports cars dont go to sleep.
There will always be anecdotal stories by people. Some will say their battery died in two days and be very upset. Others will say they died in two months. Those are the extremes. The fact is you will find many, many threads on the issue. Just do a search in the major forums.
There is a reason they suggest a battery tender in your warranty book and they sell one in tequipment, a rebranded CTEK.
is an example of a warranty booklet. Pages 11, 12, 13, 15 (including the requirement to drive the car 6K miles per year or leave it on a tender), 17, 19, and 31 all talk about keeping the battery charge and buying a tender. That ought to send a message.