I have some Pyrocat HD Part A in Glycol that is at least 12 years oldActually it's double strength to cut weight when flying when I was living abroad, Actually it keeps for around 4 years mixed in water as long as the Metabisulphite is fresh when made up. I realised this as my stock in the UK lasted while I was living in Turkey.
Ian
I tried mixing Pyrocat-HD in glycol years ago. I went through a litre of it in a month. Wasn't worth it due to very high cost of glycol. As you say, it's keeping qualities are excellent in just water (I use ditilled water).
Actually it's double strength to cut weight when flying when I was living abroad, Actually it keeps for around 4 years mixed in water as long as the Metabisulphite is fresh when made up. I realised this as my stock in the UK lasted while I was living in Turkey.

