I had a package of Hoeggers mesophilic starter thats been unopened in the fridge or freezer (its varied over time) for the last 9 years. I bought it late or mid 1999. Decided to make some Quesa Fresca yesterday- tried the starter since we didnt have any fresh- and it worked. I did use a full half teaspoon for 1 gallon milk, and when using direct set the package says to use up to 1/2 tsp. Just thought it was interesting it lasted that long.