  Long-term preservation of data and software of large experiments and
detectors in high energy physics is of utmost importance to secure the heritage
of (mostly unique) data and to allow advanced physics (re-)analyses at later
times. Summarising the work of an international study group, motivation, use
cases and technical details are given for an organised effort to secure and
enable future use of past, present and future experimental data. As a practical
use case and motivation, the revival of JADE data and the corresponding latest
results on measuring $\alpha_s$ in NNLO QCD are reviewed.
