Shopping Cart Life Span: How soon does your shopping cart expire for anonymous users? More than a few shopping systems use Session variables for tracking cart items, and expire within hours, especially for users behind prozies that change IP addresses often, thus rendering the current Session invalid (think AOL). Several studies point to the fact that customers will wait as long as 4 days before deciding to buy, and if the item they were looking at is still in their shopping cart, you just saved them several steps and increased the possibility of conversion substantially.
In professional diving, checklists are used in the preparation of equipment for a dive, and to ensure that the diver and life support systems are fully prepared before they enter the water. To a lesser extent, checklists are used by a minority of recreational divers, and by a larger proportion of technical divers during pre-dive checks. Studies have shown checklists to be effective at reducing the number of errors and consequent incidents.