Might be a good guess that the 12V battery would last longer. You would think the battery has less charge / discharge cycles. The 12V battery is charged by the DC-DC converter from the traction battery. If the 12V battery dies, I believe what will happen is the traction battery will disconnect itself to prevent it from going dead endlessly charging the 12V battery. I believe it's kind of a safe mode. Boosting the 12V battery will power the electronics, but also if the traction battery has disconnected it will allow it to assume it's safe to reconnect. I believe that is why sometimes you can't just attach booster cables and start up right away. YOu might need to let the booster battery stay connected for a while to allow the traction battery to come out of it's safe mode (I guess once it sees the 12V system will no longer drag it down below safe charge level).

Two climate control systems, one inside and the other at the tailpipe.

2007 Camry Hybrid (in service June 2006)
FE: 6.77L/100km (34.8 mpg) over 37750km (23450mi)
75% city - Ave trip 20 min - 2 Winters