Have kids lol. No, but seriously, I learnt to live with less sleep out of necessity.

I found that the amount of sleep you need is closely connected to your health. Eat healthy, stop drinking and regular exercise makes a big difference.

The rule of thumb is 8 hours but it varies wildly for each individual. And it changes as you get older. Kids and teenagers need more than adults. The elderly generally sleep less.

You can definitely do 7 regularly. Sometimes you can do 6 but pushing the limit can mean the difference between a productive day and a crappy one.