Go to User CP, on top left of the screen.
and click on edit options
then scroll down to Default thread subscription mode, and change your settings there. I have no e-mails set up, because i don't want my inbox flooded. If you do have a subscription, you can edit how often you get e-mail updates by clicking on list subscriptions, which is on the left hand side interface of options menu.
It will show all your subscriptions, and just edit how you want to receive notifications for them, and you can delete subscriptions when you are done viewing a thread.