Right, like CrazyEye said, that approach sadly doesn't really work, especially in a blowout.
Ensuring 48+ minutes in a single game obviously makes minute management for the entire team problematic. But that's one of the tradeoffs in training guys.
gotta set them as
A-B-B
C-D-D
E-F-F
G-H-H
I-I-I
for starter-bkup,reserve