I've wondered similarly . . . like using fluros 3 hrs in the a.m, then 3 just before lights out, with hps in the middle . . . to sorta simulate the cool, morning light, then waning evening rays.
Currently I'm moving hps plants to cfls for a day here and there (for space issues, not as an experiment) and all's going fine. I haven't noticed any looseness in the bud construction.