More info here:
http://forums.pelicanparts.com/porsche-911-technical-forum/900071-once-again-batterys-im-new-gimme-break.html
Summery: Battery life comes from behavior, not brand; stock batteries are way over-specced for cars that aren't driven daily in extreme weather; Deka and Braille batteries are identical—both made by East Penn; a PC680 will start the car fine.