If you've never heard the term, a persistent shopping cart saves a customer’s cart contents across sessions through “persistent cookies,” which are small text files stored on users' computers.
Persistent cookies can be used to "remember" what's in a customer's cart. They may be set to expire after a number of days or even years provided they are not rejected or blasted by the user’s browser or anti-adware programs.
The biggest benefit of persisted carts is saved sales. According to a recent study by Forrester Research, 24% of web buyers confess using the shopping cart as a wish list to save products for future consideration. Now, that doesn't mean that these customers bookmark products in the cart every time they shop online, but it does indicate that you must expect some of this behavior on the site. All of these customers expect the items to remain in the cart upon their next visit. If you don't hold these items, they may not bother to look for them again, and you lose the sale. They may also be unimpressed with the usability of your site and choose a competitor next time.
But, could leaving cart contents in tact too long be equally dangerous? Estevan asks:
How long is too long to remember your users cart information? If a user abandons cart, and comes back to site a week later, there is a good chance they will remember added something to cart. But if it’s 3 weeks later and they haven’t cleared their cookies, do you still show them products in cart? Will they have forgotten and be confused when adding another item, seeing that they now have 2 items and only wanted to purchase the most recent?
This may indeed cause confusion, but I believe a bigger problem is laziness. Like you can't count on web users to read instructions, neither can you bank on them reviewing their orders. I confess I have fallen prey to this laziness myself. As an ecommerce blogger, I often add items randomly to carts to take screen shots for my posts. One day a Barbara Walters biography arrived at my door - I didn't realize it was held in my cart when I purchased an out-of-print version of the Little Dutch Boy! Good thing it was inexpensive. Lesson learned.
Most customers don't add random items to carts, they're intentional. A more common problem is when a customer re-adds a product and doesn't realize he/she now has a quantity of 2 in the cart. "Sticker shock" may strike the customer who scans only the total price and abandons.
Another issue relates to inventory. Hot selling or clearance items may not be available 2 hours from the time the customer adds to cart. Should the item be "held" for days? How would that affect your site's available inventory? What if the price changes?
Perhaps "how long is too long" isn't the issue - it's how saved carts are presented to customers when they return.
5 Tips for Presenting Persistent Carts to Returning Visitors
Showing a prominent saved cart in the top right hand corner (big and bold, not subtle) or showing a "mini-cart" that follows the user around reminds the customer that items are still in the cart:
Set up expectations in the cart
Don't count on people reading, but sharing how long cart contents will be held at least informs customers their contents will be saved:
Show quantity boldly
Often, the quantity fades into the background of the product details, the eye jumps straight to the total and the cart button. But there are many ways you can design the cart page to draw more attention to the quantity, like putting a white quantity box on a darker background to better attract the attention of a "scanning" customer:
Showing quantity proximal to total price may have even greater impact:
Show changes to availability and price
Amazon provides clear notice when items are no longer available or have increased/decreased in price:
Use targeted selling
I have not been able to find an example of this in the wild, but another solution could be a targeted selling rule that recognizes visitors with saved items, like a lightbox greeting that says "Hello, you have items saved in your cart" and 3 buttons, Proceed to Checkout, Continue Shopping and Clear Cart. The rule could apply to all saved carts or carts that have not been re-visited in more than "X" days.
What do you think? Should there be a cap on how long to persist a cart, or should carts be presented more clearly? How do you handle persisted carts? Please share in the comments.