As far as how long the water will last in your camel bak depends on the enviroment it is in. I'm going to assume it is not in the refrigerator, but also not in a real hot & humid enviroment either. Maybe at the warmest 72 degrees in your home with the pack sitting on a shelf, a counter top or even from your bike. More then likely nothing nasty will grow in it. But I wouldn't continue to chance fate.

I highly recommend you either remember to drain it & hang it up to dry, you can purchase a special drying hanger for it. Or you at least put it in the refrigerator after you take it off, hell if you have to put the whole pack in there if you're to lazy to remove the bladder from the pack.

If your throat has been hurting like you're coming down with a cold & you can not explain why then it is probably from something in your camel bak. Gargle listerene mouthwash & the problem will soon be cured.

I've been using a camel back for 4 years now, I own differant models. After every use I remove the bladder from the pack, refill it with water, wrap the bite valve in a plastic baggie, rubber band the tube to the bladder & put it in my refrigerator. That is where all 4 of them stay until they are used. I have one complete shelf in my frig. just for the camel bak bladders. Once a year, at the beginning of Spring I use the cleansing kit that Camel Bak recommend using & give them all a good scrubbing. I just got finished with that the other day.