What happens with inactive feed users?

Stream uses fan-out on write primarily, which means if your app has inactive users, their feeds are still populated with activity from the feeds they're following (updates). To prevent this, your logic would need to determine that a user is inactive and then unfollow the feeds to prevent the updates.

Because Enterprise plan pricing is based on activities added per month, instead of updates, it matters less. In this case, the fan-out to inactive user feeds has no effect on pricing, since only newly added activities count.