Most customers use quartz or some of other type of service to periodically delete old carts after a certain number of days.

OrderSearchParameters parameters = new OrderSearchParameters();

parameters.SqlMetaWhereClause = String.Format("META.Modified < '{0}''", DateTime.Now.AddDays(-60).ToUniversalTime().ToString("s"));

OrderSearchOptions options = new OrderSearchOptions();

int records = 0;

Cart[] expiredCarts = OrderContext.FindCarts(parameters, options, out records);

Many Thanks Mark!

Marks solution is not complete and has a typo (double single quotes - thank you episerver support for this one), and the example will not work for R2 SP2. And this thread is still number 1 on google when you search for this topic.

Here is the correct solution:

var parameters = new OrderSearchParameters
{
    SqlMetaWhereClause =
        String.Format("META.Modified < '{0}'", DateTime.Now.Subtract(_ageToDelete).ToUniversalTime().ToString("s"))
};
 
var searchOptions = new OrderSearchOptions {RecordsToRetrieve = _collectionSize, CacheResults = false};
searchOptions.Classes.Add("ShoppingCart");
 
int records;
var cartToCleanUp = _orderContext.FindCarts(parameters, searchOptions, out records);