Good stuff,must have been that bucket.
So when the tds rises to 1 thats the time to put other vessel in.
So you have 2 vessels in line and get 000 but you can clean up to 10 or so,I prefer 6 or 7.
When your tds starts to rise again to 1 thats the time to change the first vessel,as it is probably at about your tap tds of 70,so is useless anyway.
Old resin goes in landfill.
So thats what I do but sometimes let tds rise till Ican be bothered to change it but ideally should be changed at about 001.