How to identify if a new tier is created because the qualifying period of the old tier expired?

I want to copy two custom fields from the expired tier to the new tier in the scenario that when a tier is expired and a new tier record is created(when the qualifying end date is passed). I have written a trigger which fires based on the condition that when the processing log field of the tier is null, copy the fields from the previous tier as this is the only unique condition I could find to differentiate a newly created tier which is created because the qualifying period of the previous tier expired. I wanted to know is there