This document summarizes findings from a survey of 97 papers on digital musical instrument design presented at NIME between 2010-2014. It identifies several key considerations for designing instruments that facilitate long-term use, such as including signature features to give the instrument a unique identity, prioritizing usability through familiar interfaces and simple interactions, choosing open and portable technologies, allowing for musical ownership through subtle user customization, and engaging in participatory design practices. While most new instruments are discontinued, the reflections provided aim to inspire more sustainable instrument design.