Age tier for closed requests

I've tried a few combinations of fields for a report that provides how long it takes for a technician to close requests broken out by some kind of threshold. For example it would provide that John Doe has closed 100 requests under 20 days, 150 under 45 days, 30 requests under 60 days, and the 10 requests went over 60 days. This is pretty close to using the age tier function but that doesn't seem to work as the age tier is relative to the current date, not the create and then close date for the request. I also tried using the number of days to complete field but I am having trouble make that work on some kind of stacked bar graph format. Appreciate any help or pointers. Thank you.