Let me preface this by stating that I normally use Amidol for my contact prints. Amidol will last for approx. 12 hours before it goes bad. I therefore do my "proof" printing when I have 35+ negatives to print, or after I have finished a session of "fine prints" (normally 2-3 hours).

This way I can do the "proofing" of my negatives once I'm tired and use my "alert" time to do my best printing.

Best