I’ve done 24h ones before and other than feeling thirsty I felt completely fine. The thing is, my urine was usually really dark/browinish and I figured I need to stop. Isn’t that a sign that you really need to drink some water?
Maybe, maybe not… but here’s an idea… do 24, then do 28, then 32, then 36… etcYour body will adapt better. It is safer. You learn your personal limits.
Why do you want to jump from 24 to 72?You wouldn’t jump from a 7 mile run, to a marathon.