There’s a lot of vague opinion here. Several studies have shown at as little as 20 mins (two 10 minute sittings) a day is sufficient to receive benefits. In fact this level of practice is the basis of one of the most popular book-based Mindfulness courses in the world (_Mindfulness: A Practical Guide to Finding Peace in a Frantic World_). 

This book is supported by scientific research conducted by Jon Kabat-Zinn at University of Massachusetts Medical School and Mark Williams at the Oxford Mindfulness Centre. 

The quality of your practice probably has more to do with benefits than the quantity. 

On an anecdotal level, I’ve personally received some benefits from one 10 minute practice a day over a period of months, but not as much as two. On the lower end, I saw no benefit from several one minute practices a day (as prompted by my Apple Watch). 

Finally, everybody can find 10 minutes in a day, even it means falling asleep 10 minutes later. 10 minutes, or even 20, may seem like an impossible amount of time to find, but one of the first things you learn, when you force yourself to make time to practice, is how much time you have to spare without realising it. Really. You’ll be amazed. 

You probably spend 10 mins a day on Facebook without giving it a second thought. It’s the practice of slowing down that makes it seem so difficult. Our mind resists at first. 

Good luck!