6 to 8 hours is only valid if you shake the dickens out of it.
Keg cold at 30-35psi and shake until you don't hear any more CO2 flowing. If you can't hear any more CO2 flowing, check the needle on the gauge, if it moves when you shake the keg, then you're still dumping CO2 in.
When you no longer see the needle move during shaking, turn off the CO2 and shake for a good 5 to 10 minutes, then turn the CO2 back on and see if you can hear it again.
When you can turn off the CO2, shake, and turn it back on again with no visible movement of the needles and no hissing through the tubes, then you know it's at equilibrium and is ready to serve. Just be sure you have long enough lines to serve at 30-35psi.