Hi, slandry.
Ok, the plugin is properly expiring transients when using your settings and your shortcode in my development environment. I wonder if something’s up with your WordPress install or the database that might be preventing some of the transients from being properly cleared after they’re set.
Do you have another environment in which you can test the same shortcode using the same settings from your live environment? If so, set up a test post using that shortcode, but set the Performance tab expiration to 1 hour instead of the default 12. Once you’ve done that, give the test post a day or so and see if it’s still working. If it isn’t, let’s get together and look at the options table of your database so we can get a better idea of what’s up.
Thanks.
James
EDIT: Also, see if you can verify whether the date and time are correct on your live server.