If you're going to carry spare AAs why not carry a cheaper, more powerful, rechargable Li-Ion backup battery?

Also, put any modern phone on airplane mode and most will last for days. GPS will still work on airplane mode!

Thus, my phone (in airplane mode) plus a $30 rechargeable pack will last for ~10 days of backpacking. It doubles as my camera, my notepad, can send text (even in crazy no-signal remote places occasionally) and can easily carry almost every map you can think of (I usually carry 4-5 maps of any given area).

I should add... my rechargeable pack also recharges my headlamp, my lighter, etc. Weight matters (to me).