Sorry, you're listening to old wives' tales.
My doctor is in his mid 40's, gets up at 5:30 am, works out an hour and a half a day, surfs, dirt bike rides, and looks like Adonis. And he has had me drinking an average of 15 - 14 oz. glasses of water a day (he drinks more, himself) for nearly three years now, and I can do things most 50 year olds can't do... and I am 70.
Of course you will keep doing what you feel is right, and that is how it should be. But the proof of the pudding is way too obvious in my life, and in the lives of most of his other patients. (Some just refuse to get with the program, and it shows to us who have known them for years.)