In all honesty, I have not used but 4 DI cartridges in the last 3 years, At 20 oz apiece thats 5 lbs in 3 years. My DI resin lasts so long I cannot buy it in bulk as the shelf life of bulk resin under perfect conditions is only 6 months and one cartridge lasts me a year. You cannot DIY something like that.

Back when I had a Watts Premier then later a Typhoon III I could use bulk because it only lasted 150 gallons no matter what I tried.