In Adobe Launch ,While creating Data Element there is option of selecting Data element Storage Duration.

Often misunderstood what this duration setting is all about and how it impact the reporting.

The Data Element will be executed every time it’s referenced. However, if the Data Element failed, then the previously set value will be returned if the duration was set to a Session or Visitor.

Consider a scenario when you would like to pass the utm_source on the landing and every subsequent page.

In this case, you may want to set a Data Element capturing utm_source with the Visitor duration. This will make the trick that the value will be returned not only on the landing page itself (when the parameter exists in the URL), but also on the subsequent pages as the value is stored (the data element code will return false, but then the storage will be checked on the value existence and if the value is there, it will be returned).