i use the bladder all the time for long hikes. After the hike i store it in the freezer. Never had any problems what so ever and had it for a few years. Now in the summer i add one or two cups of water so now i got ice in there as well. They are much stronger then they seem. The best part on those real hot days and long hikes drinking a little at the time while hiking is much easier then stoping every time to pull the bottle out of the pack. Then toward the end of the day the pack has more room as the bladder shrinks.
Sasha
Sasha