Research and practice in digital preservation requires a solid foundation of evidence of what is being protected and what practices are being used. The National Digital Stewardship Alliance (NDSA) storage survey provides a rare opportunity to examine the practices of most major US memory institutions. The repeated, longitudinal design of the NDSA storage surveys offer a rare opportunity to more reliably detect trends within and among preservation institutions rather than the typical surveys of digital preservation, which are based on one-time measures and convenience (Internet-based) samples. The survey was conducted in 2011 and in 2013. The results from these surveys have revealed notable trends, including continuity of practice within organizations over time, growth rates of content exceeding predictions, shifts in content availability requirements, and limited adoption of best practices for interval fixity checking and the Trusted Digital Repositories (TDR) checklist. Responses from new memory organizations increased the variety of preservation practice reflected in the survey responses.