My CDC told me not to worry about the 15 minutes. I make my shake up in the morning and take it to work. Sometimes I have it a couple of hours later, sometimes in the afternoon. She thought it might be because the ingredients will start to settle again, so said just to give it a shake but otherwise it would be ok.
My CDC said you can freeze the packs and it doesn't affect the nutrients...that 15 minute thingy mainly applies when adding hot water to the packs and freezing apparantly does not affect it....I have frozen them before in my IKEA ice lolly thingymebob!! The chocomint one is really nice frozen. Just give it a try...its nice!
My CDC told me when I started that I could freeze a tetra if I fancied "ice cream" Isn't freezing supposed to make things last longer and maintain the nutrients in this case, rather than destroy them?