Abstract: This disclosure describes techniques for flexible maintenance windows for performing maintenance for instances. Using techniques described herein, a user of a service provider network may specify configuration data that relates to maintenance events of instances. A “maintenance event” is any event that relates to deploying instances and/or at least temporarily losing use of an instance. For example, a maintenance event may cause an instance to be deployed, re-booted, re-started, or replaced. According to some configurations, customers may specify one or more maintenance event windows for when maintenance is to be performed, as well as customize notifications that are provided to the customer about scheduled maintenance events. For instance, customers may create a maintenance window that specifies to perform maintenance on Tuesdays, between 2 AM-3 AM, and that notifications are to include information specified by the customer (e.g., through one or more tags).