Yep, every now and then I have a batch that 'goes' faster than usual.  I try to start out very clean and be careful with each step, but sometimes, stuff happens I suppose.  I plan on making it about every two weeks, and will either bake with or eat-up that last bit if there's any left when I'm ready to make more at around the two week point.  My timing depends on when I can get to the store that I get my milk from which is not exactly on my normal travel route and sometimes it stretches to the three week mark and it's usually just fine! 

I use a milk that is "vat pasteurized not 'ultra' pasteurized.  Of course, heating the milk in the yogurt-making process may eliminate the benefits of that, but it's from a local dairy that isn't 'quite' organic, but are VERY responsible with their practices.  The big so called 'organic' companies are now owned by big corporations that I don't trust very much so I choose this local company that I trust instead, even though (or maybe mostly because) they clearly state that they aren't organic but make every effort to be smart and responsible.

Here's their link in case anyone is curious, an maybe it'll help others find similar local places of their own.  http://www.hartzlerfamilydairy.com/ 

I used New England Cheesemaking site's "good milk list" to do some research. http://www.cheesemaking.com/goodmilklist.html   

Sorry if I got carried away!  lol