On my old K-x (screen now dead), Energizer Lithium batteries would last well past 1000 shots without flash.
I used it w/o change on a 2 week vacation to Hawaii, and another 2 week trip to Alaska and this summer on a road trip to Canada (screen was dead this year - and lasted even longer
)
Pick up a cheap 12 pack at Sams Club/Costco for ~$14 as 'spare'.
Since I have the K-30 now, I did pick up a spare set of batteries off Amazon for $16, and a AA kit for $2.
AA's - never know when you need them - but can get them almost anywhere.
LiIon pack - may have to wait a while for a charge or not have your charger with you - and these batteries aren't available everywhere. For a $2 investment - an AA charger is well worth it IMHO.