I posted a formula to work out how much rennet one would need of a different known strength (i.e. I have some 750 strength rennet, and 280 strength, and 65 strength, in IMCU - I needed to work out how much of the latter two to use based upon the fact I knew how much 750 strength rennet was required), but not a "decay function" for rennet strength over time. To be honest, I've been using that 750 strength stuff for a few years now, and haven't noticed any drop in potency.

- Jeff