Did you get a fast flush for it?
If not its cheaply done with hd parts. For the first five minutes run the unit with the ball valve open. You will get low TDS
water from the start and your DI
will last a lot longer.
I would set yours up like this. (ignore the xs)
waste line -> Tee > Restrictor > Tee > check valve > waste output
xxxxxxxxxxxxxxxxxxx|__ Ball Valve __|