I'm not going to get too far into this discussion, but Xanax has a half life of about 12 hours (this and the rest of time limits are relative, not scientific).
Valium has a half life of about 12-30 hours.
Clonopin has a half life of about 16-36 hours.
Have Fun!!!
Diggs
The scientific data say:
Xanax: 8-15 hours
Valium: 20-70; major metabolite 36-96
Klonopin: 30-60