Notification event data expires after 60 seconds if no notifications get queued (see line 87 of notifications.cron.inc 6.x-2.x-dev). Under heavy load, 60 seconds is not always enough time for the notifications queue process to complete. Because of this, event data gets deleted as associated notifications are getting queued. When there are notifications in queue with no event data, generic (virtually blank) notification emails get sent out. To compound the problem, the system has no way to determine that multiple queued notifications are related to the same content update so additional unnecessary notifications get sent to the same user. To address this issue I changed the expire time from 60 seconds to 1 day. As far as I know the only downside is that event data is kept one day longer than before.

Anyone see other problems with adjusting the expire time? If not, would it be possible to change this or make it configurable through a $conf variable or something?