Pressure sealing/purging at kegging time

When I transfer from primary/secondary to keg, I like to age for a while in the cellar (50 - 60*F about 52 now) before carbonating/chilling. I like the idea of pressurizing to guarantee a good seal. So, since the CO2 is heavier than the air I should be able to purge the air just by bleeding it out through the relief valve, right? Is there any kind of method for this (length of purge, etc.)? Is it even worth while?

Also does anyone serve kegged beer at cellar temps? I was thinking about adding a couple of 'cellar temp' taps next to my keg fridge for Irish stouts and such. Maybe even a pump set-up for 'real' ales. Does the warmer temp really screw with carbonating and dispensing pressures?

one way to do this is fill the keg, them hookup the tank to the keg, set the regulator to
30 psi, shut of the regulator, purge the tank down, and repeat 3 times. this should remove all the air out of the keg. then you can store it and age it.

Thanks for the help. This should appease my OCD. Still in that noob phase where I feel the need to give everything undue attention. Hopefully that'll ease up once I've got a few batches on tap.