How long is protein powder good for once mixed?

Thank you 4Furkids, I really appreciate you letting me know what they said.  It's hard to remember things at 4:30 in the morning when I'm trying to make sure I have everything for work before I head to the gym.  I like having my protein shake ready to go so I drink it right after spin class; I only use 1/2 the liquid and add ice so the ice can melt during my class and the shake will be cold for me to drink right after I exercise.

Thank you very much 4furkids for taking the time to check into this. It's great to know that I can continue to pre-mix my protein shake!