“You have an opportunity to immediately improve your health, creativity, productivity and sense of wellbeing by getting just 30 minutes more sleep tonight than you got last night,” HuffPost president and editor-in-chief Arianna Huffington explained at The Huffington Post’s Thrive conference last week.

Given that sleep and success so often go hand-in-hand, we asked several of the seriously accomplished speakers at the Thrive event to let us in on their bedtime habits. Most, it turns out, prioritise getting plenty of high-quality sleep a night, though a few copped to scrimping. (Good thing that adding just 30 minutes per night can make such a big difference, eh?)

Here’s how many hours these nine leaders clock at night:

Dr. Mark Hyman, M.D., authority in functional medicine; founder, The UltraWellness Center:

I am kind of fanatical about trying to get at least seven or eight — mostly eight. Last night, I got seven-and-a-half, so I was on the edge.

Katie Couric, award-winning journalist, TV personality and NY Times best-selling author:

Seven.

Dr. David Agus, M.D., professor, USC Keck School of Medicine and Viterbi School of Engineering; CBS news contributor:

I get probably five to six hours a night. The key to me is not just how much sleep I get, but when I sleep. I try to go to bed the same time and get up the same time every day. It makes an enormous impact on your mind.

Randi Zuckerberg, founder and chief executive, Zuckerberg Media; editor-in-chief, Dot Complicated:

I try and get seven hours every night. I’ve found that since I had my son, I actually do that more often. Taking him through his bedtime routine around 7pm relaxes me, so I feel like I’m able to go to bed earlier. Before, I would’ve procrastinated and found things to do until 2am.

Kenneth Cole, chairman and chief executive, Kenneth Cole:

Four to five. It’s more than three or four, and I’m much more functional when I get five, than four. But I don’t usually use an alarm clock to get up. It’s this inner clock that gets me up out of bed in the morning.

Andy Puddicombe, Headspace co-founder:

Through choice, I get around six to seven. If I get too many, I actually don’t feel great. I purposely set the alarm to wake up after six or seven hours.

Laurie David, author and producer:

I sleep about seven hours — eight would be better. But I wake up, no matter where I am, at 6 or 6:30am.

Lucy Danziger, former editor-in-chief, Self Magazine; wellbeing lifestyle expert

Last night I got about five-and-a-half, but that is not a good enough amount. I always say, “Invest in tomorrow by going to bed earlier tonight.” You can stay up and watch re-runs of “Friends,” or do stupid things on your computer, but tomorrow you’re going to be wiped out. Seven hours is good for me.

Panache Desai, spiritual teacher:

Eight hours, 10 hours. I love sleep, it’s one of my favourite activities. I attribute sleep to my success.

These interviews have been edited and condensed for clarity and length.

This article originally appeared on The Huffington Post and was reprinted with permission.