[Dovecot] Post-login scripting - Trash cleanup

We are considering using the post-login scripting to clear trash older than 90 days from user accounts. has anyone done this, and if so did this cause logins to slow down too much waiting for the trash to purge? One idea was to execute the trash purge script once a day by tracking their logins and seeing that it has already ran that day. Another idea was to call the trash purge script in the background and continue without acknowledging that it has finished to keep logins speedy.