They have already been supporting both for a while. Presumably they would like to go 100% to the new workflow in their sorting centres. A longer swap period me

They have already been supporting both for a while. Presumably they would like to go 100% to the new workflow in their sorting centres. A longer swap period means more expensive equipment sat there doing nothing or longer period of time supporting two different workflows. Also the distribution of stamps held; people who post a lot - 0 swaps needed. People who hoard - have multiple years supply. People who dont post often at all but have stamps sat around - 10 years supply assuming you can find where that 10 pack of stamps is. 6-12 months to restock all outlets and have companies wind down their supplies of old stamps, and a good amount of time to test the new workflow on an increasing volume, while still being able to back off if the system blows up.