I think it says on the tub that once dissolved in water it should be consumed within a day or so. If I have it after a week will it kill me? Are they just covering their backs or should I listen to what they say?

36 hours in my experience.
Much more than that and you are running the risk of turbocharged guts.

(i sometimes make two bottles and have one left over after the ride, so it goes in the fridge for the next days ride. After that it goes down the sink)

I’ve tried 48 hours before, never again.

Till it grows

Cheers, I’ll chuck it and not take the risk!

Turbocharged guts 🙂 that made me laugh