Are there any form of limits that come with this by default? For example, a thread that's had no replies in X days/months/years but is still being watched by X users could be considered useless.
Some forum owners disallow the bumping of threads, so as soon as the "Do not reply to a thread if it has had no replies in X days" marker is reached, nobody would reply to that thread again. If this happens for 1,000 threads for example, we could possibly have X users watching 1,000 threads which will probably never be posted in again, making the alerts useless and the database having this info also useless.
Some forum owners disallow the bumping of threads, so as soon as the "Do not reply to a thread if it has had no replies in X days" marker is reached, nobody would reply to that thread again. If this happens for 1,000 threads for example, we could possibly have X users watching 1,000 threads which will probably never be posted in again, making the alerts useless and the database having this info also useless.