I'd suggest making a name available for the pickups after a month of inactivity, but without deleting the account. Basically if the name does indeed get taken after that month, the user of the taken name gets to choose a new one on their first log on.
I saw this sort of mechanism in several places before.
You can also set up so that the followers of the account that has lost its name get an automated message and/or email, and the account gets temporarily suspended (until holder decides on a new name) or renamed to some random gibberish (randomly generated usernames. Temporarily, of course).
I'd suggest making a name available for the pickups after a month of inactivity, but without deleting the account. Basically if the name does indeed get taken after that month, the user of the taken name gets to choose a new one on their first log on.
I saw this sort of mechanism in several places before.
You can also set up so that the followers of the account that has lost its name get an automated message and/or email, and the account gets temporarily suspended (until holder decides on a new name) or renamed to some random gibberish (randomly generated usernames. Temporarily, of course).