In our situation we also always remove the Bill of Material for this assembly,  (Redlining)   The lifecycle of the part is set to obsolete, the bom is emptied.   In this case when a whereused is done for a component this part doesn’t show up anymore.   When the obsolete assemby is used in a Bill of Material, the parent needs to be revsioned, to take out the Obsolete item.  Next to that it is not allowed to release an item with a component that has not the correct lifecyle (Obsolete is not a correct lifecycle)

In Agile 9.2.2.4 there are some standard reports that you can use :
1.  Change Backlog Report that :  Counts the changes that were at a specified status but have not moved to another specified status during a time period. 
2.  Cycle Time Report that : Determines the time it took changes to move from one specified status to another during a time period..
3. Change Metrics Report : Counts the changes that were moved to a specified status during a time period.

In our System the ECO is used to releasee DMR objects (Parts and Documents) an DCO is used to release DHF objects.
The difference is made due to the fact that the DMR Objects need to go to the ERP system and DHF objects are only present in Agile.
The next reason why we have created multiple change orders is the difference in the workflow.  In the ECO the workflow steps are different that in the DCO.

Agile has a very nice searching ability. When you know that the search shall be used multiple times, save it as a personal search for the user.  When there is data in the search that can be different every time you run it, make it a POP-UP, so that every time the search is runned the user can give in what he/she eants to search.