I've got a k100d and bought it because it uses AA batteries. Best non-rechargeables were Energizer Lithiums (seemed to go on for ever). My rechargeables weren't very good at all (can't remember how long they lasted) but I soon heard about Eneloops which were marvellous - rechargeable and last for ages and ages! There are also plenty of other batteries with similar technology now too. At least I know that, in an emergency, I can pop into a shop and buy a set of 4 AAs and keep going.

In the past, I had a 35mm Canon and went to the USA. Needed a new battery, so had to find a photographic store. Got new battery but it cost a fortune, much more expensive than we paid in the UK at the time. Would have been much easier & cheaper to pop into a store for some AAs.