Notifications are an essential feature of smartphones. The notification drawer is the central place to view and attend notifications. Although a body of work already investigated how many and which types of notifications users receive and value, an in-depth analysis of notification drawers has been missing. In this paper, we report the results of a large-scale observational in-the-wild study on mobile notification drawers. We periodically sampled the notification drawer content of 3,953 Android devices, resulting in over 8.8 million notification drawer snapshots. Our findings show that users have, on average, 3.4 notifications pending in the notification drawer. We saw notifications accumulate overnight and being attended to in the morning. We discuss the prominent positioning of messaging notifications compared to other notification types. Finally, inspired by prior work on the management of email inboxes, we propose the three user types "Frequent Cleaners", "Notification Regulators", and "Notification Hoarders" and discuss implications for future notification management systems.