On my '04, I had it parked for about half an hour with no A/C or heat, just fan and radio going. It *DID* discharge into the pink/purple zone, and the engine only ran for about two minutes (long enough to get to the blue zone.) I then started driving again before it dropped into the pink/purple again.
A few days ago, I started the car and it was at only three bars, and turned on the A/C. Because of various delays, it ended up being a few minutes before we got to driving, and with the A/C going, it dropped the battery to two bars before we started driving. Again, the ICE only came on for somewhere around two minutes. (Again, I started driving before the battery dropped down to two bars again.)