[Amps] Tube Burn In Question.

[ab5mm]

The 20+ year old 3-500Z Eimacs have lost their brilliance. I finally 
broke down and purchased a new pair to go into the Henry 3K-A today at 
HAM-COMM.
My question is how should I "burn in" the tubes?
How many hours?
Only filament and blower on? (I did the mod to cool the pins)
Filament voltage? (I can vary it)
And finally, is there a general consensus on whether or not some portion 
of the burn in time should include plate voltage (no drive, just idle 
current? (I can vary this also)

As always, Thank You for the input.

Steve
AB5MM