different serving pressure from carbonation pressure - two tanks and regulators

Brewing Processes
1

If I had two separate co2 tanks and regulators and set one to force carbonate my kegs at 10-12 psi for say a week to 10 days at about 40 degrees, then switched the gas in line to a different co2 tank with regulator set at lower pressure for serving perhaps 2-3 psi, would the co2 slowly diffuse from solution and eventually result in the beer having a lower level of carbonation, ultimately equivalent to 2-3 psi? would the beer last long enough to find out?
okay, any ideas about the first question?

2

Yes, eventually what you say would happen

3

The CO2 would slowly diffuse out until the carbonation level was equivalent to 2-3 psi.  Assuming that the actual pressure inside the keg drops immediately to 2-3 psi, I would think that you might notice that the beer is undercarbed as early as the next day.

It sounds like you should use longer tap lines to create a backpressure of approx 10 psi.

4

Thanks. Kinda what I was thinking. I have 10 foot lines on my taps but as it gets near the end of the keg things get sort of foamy. I am expanding from a four line distribution to eight, so I considered doing the second regulator, as I will mostly have one keg tapped and the second one standing by. I recently reworked my beer fridge to hold twice as many kegs - gave up bottling for the life of ease. again, thanks for the input. I suppose I can consider the increase in perceived pressure a sign that kicking is near - a sad day.

5

it will happen, but may or may not happen quickly. if you have the beer in the keg equalized at 30 psi, and if there is a lot of head space already with pressure at 30 psi, this may take a bit.  when you switch to the 2 psi regulator, that regulator should, as i said, should remain closed.  in other words you are not going to open and supply 2 psi gas to the keg until that head space pressure drops to 2 psi. if you have a lot of head space and pull off a beer, the pressure will drop and equalize as co2 comes out of solution to a new slightly lower pressure. with a lot of head space and high pressure this could take a bit.  if the keg is completely full with liquid it will happen faster.  ex.  a 15 gallon keg with 10 gallons in it and head pressure of 30 psi, drops to 5 gallons of beer, and now 10 gallons of head space the pressure would drop to about 15psi i say about because that is just a basic pv=nrt without discussion of gas in and out of solution.