The Forgotten On

Optima started having issues with their batteries when they moved production from here in the US to Mexico a few years back.

I stick with good old lead acid like almost everyone here uses. I replace it every 6 years or so in the 928s without issue.

Schocki

Regular lead battery in my GTS with no issues. Bought from a regular car parts supply store, 72 Ah like supplied by Porsche. I can let the car sit for about 3 weeks without charging, it'll turn over and start just fine. After three weeks I have to hook it up to a regular charger and it's good for another three weeks.
Last battery in my GTS lasted 7 years but started to have trouble starting the car after two weeks, so it was replaced. I don't like to get stranded if preventable .

slownrusty

Granted AGM's do not like to be deep cycled.
My AGM sits with a maintainer and never had a problem. I'm running a tiny motorcycle AGM on my 930 and its been in the car for 5+ years.