I think a day or so is fine for your dry fasting.I think if you start trying to set new records you could DIE! If you read most survival manuals think around week most people die from no food and water.You can go for months if you are fat on no food. Course there are variables on how quick you die on water. Things like temperature you are in,how much you are exerting and sweating.
Dehydration is not that pleasant and some symptoms of it could be pretty dangerous depending on what you are doing.
I say limit your dry fasts to 48 or so max and don't try to be some scientist trying to set new records. But hey its your life.