I used to buy Fleischman IDY in the one pound package and store it, well sealed in the freezer. I used it once a week and it would keep well for over a year.
In the Fall of 2012, because of this website, I decided to try new approaches to my crust. Every Friday night, the crust was blah, the family looked at me and said "Why don't you go back to the original crust?" I even tried that again and blah! This went on for two months, it was terrible.
Got involved in one thread here about yeast and posted my problems. Chicago Bob posted and said "Why don't you go to the grocery store and buy a single packet and try it to see if it works". I did and everything was back to normal, the crust flavor and texture was back etc. The family was happy.
I subsequently used the yeast from the freezer, it rose as it should but the crust it made was terrible. Obviously the IDY somehow became contaminated in the freezer. I now buy the Fleischman IDY in 113g jar for $5+, very expensive but pizza is too important to take chances.
One possible source of the contamination could be my winemaking in the basement, yeast and malo-lactic cultures are involved and this goes back 24 years, the house must be infested with yeast cultures. I am currently fermenting a premium California Cabernet Sauvignon we picked up frozen, last week, from M&M in Hartford CT. I doubt the pizza will taste like Calif Cab
Still think Chicago Bob is a genius, thanks again Bob.