I have my setting to subscribe when I reply to one. But, I often will get tired of certain discussions which fail to continue to hold my interest and unsuscribe. Also, if a thread grows too fast, I will unsubsrcibe to save the ham§sters some grief and just follow it along without the e-mail reminders.
Even with the purging I do tho, I still have 3096 threads on my subscription list.
How about you? Do you subscribe? What type of notification (instant or daily)? Do you purge? How many on your list? Do you ever go back and reread any of the older threads?