CO2 Blanket / Keg Question

[TriggerFingers]

So I am aging an Imperial Stout on oak in a corny keg. I purged it very well (about 2 minutes open with the relief valve open) with CO2 a month ago. A friend of mine seems to think that the CO2 needs to be added each month or so to keep the blanket intact? His experience is that when he pulls the relief valve, there is no longer a hiss coming from the keg.

However, that doesn't make sense to me. If the keg is blanketed, then wouldn't the CO2 eventually absorb in the solution? Just because there is no longer a hiss doesn't mean that the CO2 escaped and O2 got in.

My questions are:

Am I correct that the CO2 blanket is still there?

Do I need to add more CO2 to the keg periodically if storing for 6-9 months.

Thanks!

 

[day_trippr]

The head space pressure is diminished because nearly all of the introduced CO2 is absorbed by the beer.
But as long as the keg was sealed tight, oxygen ingress is a non-issue.
No need for periodic recharges...

Cheers!

 

[DemonsRun]

day_trippr is correct, however if you keep checking if the pressure is still there, you will eventually need to re-pressurize. So If the Beer was not carbonated, yes it would absorb the C02 and appear to not be as pressurized. But a pressurized Keg of carbonated Beer will not loose pressure unless there is a leak.