Whatever you do, don't talk to OnStar about this. I continue to not really understand what we lose after 3 years (or even 8 years) so I called them. The sales guy said we lose entertainment apps like "Spotify and Hulu" at three years. Yes, he said Hulu. He also said we lose Google maps and the Google assistant ("Hey Google"). He also said we lose "wifi", but we finally agreed that he meant i ternet access. When I asked specifically about ABRP, he said we keep that because finding chargers is " necessary to operate the electric vehicle". He also said the 8 year plan is renewable at no charge. He was sure you can't renew it for 8 years, though. He thinks 1, 2, 3 or 4 years. He said if we needed the 3 year functions today, he could sell us a plan for just $24.99 per month and it includes data and using OnStar as a wifi hot spot. None of this made sense to me so I asked for a list of the app store apps we will lose at 3 years. He said he couldn't provide that, but he thought the tech folks can.
The lady at tech said we retain the Google Assistant and Google maps after three years. She knows someone using just the basics w/o app support and can confirm that. According to her, all we lose at three years is "entertainment apps". But she could not give me a list. She referred me to Chevrolet.com. I couldn't find any more detail there even when I signed in.
I think I've given up. I'll find out in almost exactly two years what we lose. Maybe someone who bought earlier will share his/her experience when their 3 years is up.