Kirkland batteries are reasonably priced and long-lasting; about 5 years has been the typical life span for us, though the spec is 8 years.
Costco won't install batteries but will dispose of the old ones. The doughty do-it-yourselfer only needs an adjustable wrench or set of wrenches and perhaps a screwdriver. The whole process used to take hours--buying the new battery, shuttling home for removal and installation, and returning to Costco with the old battery and receipt (to get a free disposal).
Lately I've been bringing the required tools to Costco and performing the installation in the parking lot. The whole swap has been cut to half an hour, and I've learned to ignore the quizzical looks from shoppers in their upscale vehicles. Yes, I used to look askance at people who worked on their cars in parking lots, but now I'm that guy. © 2014 Stephen Yuen