A few months ago I had a gallon of milk in the back of the fridge that stayed fresh for over a month - maybe even two; I lost track. Our house is only me and my wife.  We don't drink milk often.  I use it more for recipes, and maybe an occasional iced coffee.  Since I couldn't repeat this feat I have gone to half-gallons. What I noticed about this gallon in particular is that its plastic container was more opaque than what we normally had been getting.  Previously I was getting the supermarket brand with the semi-opaque plastic container.  I had gotten this one, white, 100% opaque at another store. I also thought maybe it had something to do with it being in the back of the fridge.  Also, being packed in by other fridge mates.  But this is something I have always tried to do. Are there steps to try to get milk to last this long?  Especially since I don't use it that often. Further Clarification: There seems to be some question about how spoilage was determined. I have always and forever smelled my liquid dairy before using.  I stand by my nose to let me know when such a product has gone too far.  In some cases I have chosen to go a day or two beyond the onset of spoilage.  This onset can be detected by a sweet-sour smell. In the instance of this gallon I have posed above, there was no such indication in smelling the milk for at least a month beyond the Best By date.  Of that I am sure.  There was a period when I hadn't used it.  After which I smelled it and it became obvious it was too far gone. 
Milk goes bad because it gets colonized by bacteria.  There are two sources for this bacteria; ones already present in the milk because pasteurization didn't kill them, and from the environment (that is, bacteria in your fridge). The "expiration date" for milk is therefore a conservative estimate of the time when the milk might start turning bad.  Note that many political regions have specific regulations on setting those expiration dates, which might cause them to be set way early from a probability-of-spoilage perspective. Thing is, that probability-of-going-bad date is more of a half-life, and many factors can affect when it actually goes bad.  And just like milk can go bad early because of those factors, it can also go bad late.  Particularly, in this case, I'd guess that pasteurization of the milk was unusually effective, and either you didn't open the milk or your fridge is exceptionally cold and bacteria-free. I, too, have had some dairy products last for weeks beyond the expiration date, particularly half-and-half.  However, you can never count on it. If you're looking to maximize milk lifetime, then, you create the best conditions:  Find brands whose pasteurization seems to be extra-effective Keep your fridge cold and squeaky-clean Open the jug/carton as little as possible Never leave the milk out on the counter Don't drink straight from the carton.  Seriously, did your mother teach you nothing?  Jeez.  