Resale value for guidebooks drops substantially when a new edition comes out, like the textbook market. Like textbooks new editions don't mean that much has changed inside - Lonely Planet has become particularly bad about updating their information. This doesn't stop them from churning out new editions for hot tourist destinations - a new New Zealand or Australia guidebook appears every 9 to 12 months content mostly unchanged, where S. American destination go 3-5 years between "updates".

The actual useful lifespan of the guidebook depends very much on how much the destination has changed since publishing. With burgeoning tourism it doesn't take more than a couple years for the guidebook to become less than useful. As an example the Lonely Planet Argentina was practically worthless for Ushuaia, AR because the town had doubled or trebled it's tourist capacity since the guidebook was published. Eateries were gone, hostels changed owners, locations, or simply closed up shop, nightclubs changed, etc. Coupled with flat out wrong maps and you've got something that isn't much help.