Spunding Valve

Been trying to think of an ideal setup to age a sour beer in a corny keg following primary fermentation that would allow a small amount of pressure to remain on the beer (a few PSI) and minimize O2 as well as allow for easy sampling over the planned several month souring/aging process.  I fear with carboys I will have an excessive amount of O2 exposure with sampling as well as a more cumbersome sampling process with a thief several times over the course of a few months.  The idea of using a corny keg slightly pressurized to keep O2 out and ease of sampling with a picnic tap (or similar) and a shortened dip tube came up.  Then I worried about excessive pressure building up as Brett/bacteria works their way through residual sugars if I were to forget to pull the relief valve often enough.  I came across this valve on More Beer.com which seems to offer a potential solution.  I could set the PSI fairly low (3-5) and any excess CO2 would simply blow off with no risk of O2 entrance.  Does anyone have any experience in a set up like this or does it theoretically make sense?  We are sometimes away from the house for weeks at a time and this would be seemingly a good way to set something and not have to worry about it too often.  Any idea of how Brett and bugs act under a very low PSI head pressure?

That should work as long as the spunding valve is functioning properly.  I have a spunding valve that is similar to the ones that morebeer sells which I use for a couple of different applications.