I've never had a true Nalgene 32oz widemouth leak (off brands have) so I consider the risk with it minimal. Efforts to constrain weight, cost or both don't always allow for you to have what you need plus safety margin. If a night turns colder than forecast, a hot water filled Nalgene in the hammock is an effective and easy solution. Not sure I'd try it with other products. Have seen too many people get leaks in their Platypus and other bladders.