That's a great trick - will have to give that a try. I imagine that you put the cryo hops in a weighted bag to get them to stay submerged?
It takes me a while to go through a 5 gal keg and a hoppy IPA sometimes starts to get less special (flavors and aroma get more muted) after several weeks of being on tap, even with all the little tricks to avoid oxygen pickup. On a recent batch, I carefully bottled the first 2.0 gal to see if those hold up better over time, but can't see why they would. If anything, the bottling process added a tiny bit of oxygen. Maybe I just need to invite people over when fresh and enjoy when at peak.