The Vivaldi comes with a spare set of screens so that you will always have a clean set & "hopefully" change them regularly. The 2 screen design is supposed to trap the grinds & keep the 3 way valve cleaner so chemical backflushing is only necessary once a month. Seems to work as I seldon see grounds above the upper screen.

I do plain water backflushes 4-5 times a week, change screens/clean dispersion block once a week & do a chemical backflush every 4 weeks. While on the subject of cleaning don't forget that Mazzer also needs regular cleaning or you will end up with rancid grounds in there. I vacuum out the hopper/upper burr area, doser & chute at least once a day & remove the upper burr carrier on my Macap for a thorough cleaning once a week. You will find lots of old grinds packed in around the burrs.