In the past, there have been spells (a day or so) in which I don't get any alerts, and then a slew (sometimes 30+) all at once. This last Sunday, I got nothing for hours, and thought that the threads I subscribed to would be more active at the weekend. Today I haven't received the whole backlog as in the above described scenario, but rather alerts of the most recent post for some subscribed threads. I am getting a lot of these today. I go to the thread and find several (a few, up to maybe 15 or 20) interim comments from over the last few days for which I haven't received notices.