I recall Russ stating at the RO/DI meeting that recharging DE Resin is not cheap and/or easy to do? In any event, carbon and a pre-filter will not protect the DI resin that much....not like a RO membrane would. Eco friendly yes but labor intensive as well.
If anyone is interested in Nuclear grade DI Resin, I am bringing some to the swap for sale (listed on fragswapper.com)