All AA NiMH cells are not created equal. Some have higher capacity than others. Read the packaging or labels and try to find a capacity of 2500 mAH or better. Some old AA cells with 1600 mAH capacities are still being sold out there. That's considerably lower.

One downside to NiMH chemistry is the high self discharge rate. Your freshly charged cells will lose about 10-15% of their capacity in 9 days. The new Sanyo Eneloop NiMH cells claim a far lower self discharge rate for a little more money. In my experience their claim seems to be valid.

Invest in a good quality "smart" charger. Avoid cheap "dumb" chargers that rely on only a timer for a fixed charge time regardless of the cell's state of discharge. Some don't even have a timer and will fry your cells very quickly if left in too long. The better chargers rely on the cell's voltage, temperature or both to terminate the charge cycle. The better chargers will also ensure that you leave home with fully charged cells by not terminating the charge cycle until the "tank" is full. Some cheaper chargers may terminate before the cell is fully charged. And some older chargers are not designed to fully charge the newer high capacity cells.

Buy your cells well before you leave and run them through several charge/discharge cycles. This breaks them in and even slightly increases their capacity. This practice also reveals the dud cells, which are not terribly uncommon with some brands.

I have found Thomas Distributing to be a good online source for cutting edge cells and chargers. Their website will show you what's out there even if you don't buy from them.

360 shots with the LCD screen on sounds very optimistic to me. Maybe with freshly charged (same day) high capacity cells, no flash, no timer and no auto preview, but I would not rely on that figure.