Workflow actions remain in the time-based workflow queue, even after the triggering criteria changes

Situations where the action will not automatically leave the queue:

• The initial record no longer meets the triggering criteria due to a Workflow rule field updates, where the "Re-evaluate Workflow Rules after Field Change" check-box is not ticked.
• For Process initial record no longer meets the triggering criteria, where the Recursion - Allow process to evaluate a record multiple times in a single transaction.
• The initial record no longer meets the triggering criteria due to the record naturally falling out of the triggering criteria, due to e.g. a time frame lapsing

           Example: if the Criteria is "Created Date = TODAY() "

The day after creation the record will no longer meet the triggering criteria, but there will be no edit involved in this change - as such any time-based workflow actions that the workflow had placed in the time-based workflow queue will remain

Apex DML field updates will usually re-run the workflow rules post update, and remove the action from the queue. It is recommended this be tested first though, if an Apex update is going to be considered as a method of ensuring the triggering conditions remain 

As a workaround to this it is recommended that if another Workflow rule field update is causing this issue, the "Re-evaluate Workflow Rules after Field Change" check-box in the field update should be ticked. When using time-based workflow the triggering criteria should be carefully analysed to ensure that a naturally occurring drop-out, such as "Create Date = TODAY() " cannot occur.