I start tasting after 4 weeks of cold storage in kegs. I find my IPA's are at there best between eight and twelve weeks. Bottling is so time consuming that I have abandoned it completely. I use small kegs or growlers when I want to transport.

I have been buying CO2 from a welding shop which is substantially cheaper than AirGas. So I assume it's welding grade. My IPA's still taste fresh after 6-9 months in the keg. My lawnmower beer starts to show mild oxidation after 3 months. Maybe I should switch to beverage grade.

Just curious. Did you purge the kegs after sealing them up? Also I have read that CO2 tanks can be contaminated with small amounts of Oxygen, maybe try a different vendor.

I have been using a long stem instant read (bi-metal) from Morebeer. The accuracy has been very good and it was calibrated straight out of the box. I checked with the ice water and boiling water. It has a 12" stem and a 2" dial which is easy to read with my cheap magnifiers. Not cheap, at $27...