I agree. But this is not really 70% when you're doing garbage drugs, boozing, and eating like shit 2-4 days a week, and then dealing with the consequences until wednesday. Which btw, you certainly will be dealing with them if you're outside of your mid to late twenties. 

70% is like not getting any exercise on the weekends, having a binge night 1-4 days out of the month and then having a couple of drinks on another 4 nights out of the month.

If you're 20 years old and your only responsibility until tuesday is to make it to your history of polka dots seminar at 11am do whatever TF you want as long as you dont develop any habits that you can't manage or afford.