Re: How long does milk last, before it spoils, in plastic milk cartons?

Hello David!  Good question but it will be best answered by some 
experimentation by you.  I can give you a few hints to help you design your 
experiments though...  Milk will spoil faster or slower depending on a number of 
different things:

how much bacteria is in the milk (whether you've opened the carton or not),
what kind of bacteria is in the milk (whether you drank out of the carton or 
not), and
the temperature the milk is stored at (whether you put the milk back in the 
fridge or left it on the counter)

Each of these factors will affect the rate of growth of the bacteria in milk and 
 so the rate at which it will spoil.  But you will have to find out for yourself 
how long it will last under each set of conditions.  :)

Good luck!

Kieran