One comic I used to follow handled it this way: Every new update was a new episode, so that everyone got a "new episode" notification like normal. Then, after a few updates, they'd combine a bunch of them into one episode, deleting the extras.
To explain in more detail, they would start out updating like this:
- Episode One: Page 1
- Episode Two: Page 2
- Episode Three: Page 3
- Episode Four: Page 4
- Episode Five: Page 5
and then edit it like this:
- Episode One: Page 1-5 (edit the episode to add pages 2, 3, 4, and 5 to it)
- (Delete Episode Two, Three, Four, and Five)
so that their archive would eventually like sort of like this:
- Episode One: Page 1-5
- Episode Two: Page 6-10
- Episode Three: Page 11-15
- Episode Four: Page 16
- Episode Five: Page 17
- Episode Six: Page 18
and then once they got to page 20, they'd combine 16-20 into Episode Four and delete the extras.
This means they would lose the comments they'd gotten on the episodes that get deleted this way, but to them, it was worth it to keep their archives from having too many episodes -- and they figured the comments had been around long enough that everyone had gotten a chance to read and reply to them.
You don't necessarily have to do that, but it's another option to consider if you don't want to change the way your archive is laid out, but also don't want to lose mobile readers who won't get the edit notifications!