I've been using the same 2 ozs bottle of FermCap for the past 2 years. It's almost finished. I use it for both the boil and in the fermenter, and it has worked great preventing boil-overs and blow-offs.
My last 3 beers have all come out the airlock (WLP550 - PacMan - WLP 550). This latest one I used my blow-off tube. I haven't needed a blow-off tube for a long time, and getting 3 in a row that want to crawl out of the fermenter is getting me thinking. I know Belgians tend to ignore FermCap, but the PacMan did it too.
Also, when brewing the latest beer I was concerned that it might actually boil-over. It was not as stable as normal.
I assumed that since this stuff was silicone based, there was no shelf life (despite there being a note to use within 1 year on the label).
Anyone any experience.