Content availability has become increasingly important for the Internet video delivery chain. To deliver videos with an outstanding availability and meet the increasing user expectations, content delivery networks (CDNs) must enforce strict QoS metrics, like bitrate and latency, through SLA contracts. Adaptive content replication has been seen as a promising way to achieve this goal. However, it remains unclear how to avoid waste of resources when strict SLA contracts must be enforced. In this work, we introduce Hermes, an adaptive replication scheme based on accurate predictions about the popularity of Internet videos. Simulations using popularity growth curves from YouTube traces suggest that our approach meets user expectations efficiently. Compared to a non- collaborative caching, Hermes reduces storage usage for replication by two orders of magnitude, and under heavy load conditions, it increases the average bitrate provision by roughly 90%. Moreover, it prevents SLA violations through an application-level deadline-aware mechanism.