The Manoan prep uses three cycles of one minute each, seems to work well. And for my krunk prep I only do 30 seconds per wash.
The one time I tried a full 4 minute blend then strain, the kava was too strong, IMO, in part because it had way too much particles in it. I think what we want is to shatter the particles a bit to release the kavalactones and leave a lot of the lumber in the makas, not break all particles so fine you drink them all.