Check out Bhandari’s 10 commandments – http://tinyurl.com/aaxjehy
My favorite “To Have and to Hold is Good, but not til Death Us Do Part”
Recommendation is not to keep data indefinitely because storage is cheap. When you get into dispute the cheap storage suddenly becomes expensive since you might have to collect at source and have it reviewed by lawyers. Vendors with Predictive coding technology have the foundation to build a solution for defensible deletion and reduce the volume at source.