Have you ever heard of ProccessLead time? Process Lead time is the amount of time between the start of a process and its conclusion. In other words, it’s the amount of time from a card creation until it reaches an end phase of the process.
To check you process lead time For that, you must create a report with the following information: : “Created at” and “Finished at”.
After selecting both columns you can export it to excel by clicking on 
Nexct, open the Excel file, add a new column called “Lead time” and on the cell add the following formula: =Finished at - Created at
The result will be the number of hours or days a card spent to go from the first to the last phase of your process. You can apply this formula to all records of cards in the spreadsheet and at the last cell you must add the following formula to get your process lead time: =AVERAGE(cells range)
The final result will be your process lead time..
Ps. It’s important to mention that for cards that aren’t finished yet, time is still counting.