too much TDS?

[Graham_f]

I know its time to replace the filters in my RODI filter... but how much is too much for TDS?

When my filter system was new i had a 0ppm reading for a few weeks, then it just kinda sat at 2ish ppm for the next 8 months.
Now suddenly im up to 26! Time to get new ones

How often do you change yours? Is 0ppm for the life of the filters realistic?