I have been on double DI for 3.5 years now, I think I was one of the first to post on it. Tap TDS around 55.
I will have to try this stirring though, I have been a bit lazy on this one, just binning the resin in the first cylinder when it read the same tds as tap water.
Don't do what I did last week and leave the water on all night, flooded the back yard with pure water, and it was still reading zero on the tds meter.