Automatic persistent shopping cart

Client wants customers who leave the site and return later to keep their shopping cart contents. Shopping on the site is private and requires a user login so all shopping is done by a registered user. I've noticed the cart contents stay if I navigate away from the site and return, but how long will the session hold that contains the cart contents? Secondly, I noticed when the user logs out, all the cart content disappear. We'd like those contents to be 'saved' in some way so when a user returns, the cart contents are still there for them to complete an order.

You can use the Save Cart Details In Database server behavior to save the cart contents into a "ShoppingCart" table and then retrieve the cart contents from that table when a user logs in.

This is something I could help with in a premier support ticket.

Two clarifying questions:

While you're browsing the site how are the current cart contents temporarily stored, and more importantly when or what triggers the expiration of that data? I noticed if I leave the site and come back, the cart contents are still there, so long as I do not log out of the user sign in.

Secondly, with what your suggesting, how would the save be triggered? Every time they add to the cart?

The cart is saved in the session by default, so it will stay as long as your site defines a session to last or until the user closes his browser window or logs out.

Every time they add to the cart is probably a good time to update the database to save a fully persistent cart. Another option would be to use a cookie based cart. That would save it for the current browser and could be set to weeks or months, it just wouldn't be tied to the user if they were on a shared computer.