Hi Taun,
I have just run a test case with my own subscription set to expire on the 15-05-2015. I set the reminder emails to go out at 30 days and 14days before expiry. I set it to remove it from one group and assign another on expiry.
I must be doing something wrong, I have received no reminder emails and the group settings haven't changed although the subscription is showing expired.
Have you any suggestions?