- 10,000+ hours for basic competency
This you can accomplish with ~3 hours of training daily for about ten years. Here I'm talking about internal technique, as opposed to being able to do forms well and properly, or beat non-masters at push hands via brute strength.
(Even the push hands competitors aren't quite yet doing it internally b/c they're just too young—it's grappling using Tai Chi movements as opposed to Tai Chi technique.)
This is why traditional Chinese schools start with external arts, to provide something serviceable in addition to the baseline strength required to practice internal.
You can teach internal forms to kids, but there's really no point until at least the late teens.
Most practitioners are unable to even relax enough until the body starts to decline in the mid-30's, such that brute force is increasingly less effective. (My sense is that true masters, even in external styles such as Karate, naturally become "internal" after a sufficient number of years.)
Lifting weights is not generally recommended, although old school training involves brutal "basic training" (calisthenics), and can involve extensive isometrics, heavy stone balls and heavy weapons.
"10,000" is about where you can start to so some stuff using real technique, but any believing they can "guarantee everything 100%" is fooling themselves. It typically requires training with a high level master to understand this, i.e. someone who can "set the student straight", because serious students are strong, fast, and know a lot of applications.
My teacher's generic answer for how many repetitions were necessary to master a single given technique was "a thousand thousand times" and this was to be taken literally.
- 30,000+ hours for a basic level of mastery
My teacher did this in the first ten years, "ten years, ten hours of day". This is literal, because it's all they ever did from early childhood, although training in the internal arts only began in the late teens.
This was the interior of China, where there was no television, limited access to electricity, and very little else to do except hard labor. The teaching involved living with the master of a top lineage. This was ~4 hours in the morning, ~4 hours in the early evening, including teaching "outdoor students", and private "midnight practice" with the master every night.
My teacher didn't even have hobbies until later in life, and still trained 4-5 hours per day, with the rest of the time teaching private lessons, and pretty much only thought of that. (I had the privilege of meeting Jimmy Pedro, and it was refreshing to meet a martial artist who had never even heard of my teacher. Pedro explained it "I only know Judo" i.e. "I only think about Judo. I only care about Judo." Malcolm Gladwell has written about Wayne Gretzky being similar.) I suspect that first ten years for my own teacher included many days closer to 12 hours.
(It took me 30 years to get close to that number of hours, and I still don't call myself a master, because I'm comparing myself to the best of the best of the old school. I had a career outside of martial arts, so I trained ~4 hours per night when not traveling, plus short morning practice, with up to ten hours and teaching on weekends. When traveling I'd utilize empty hotel conference and ballrooms, around hotel pools late at night, and sometimes in parks, or, when not available, in the hotel room itself, tailoring practice to available space.)
- 60,000+ hours for a high level of mastery
That covers the 30's and 40's for an old-school, full-time practitioner, such that, by 50, one who has devoted their entire life to it is usually at their peak in the middle of life.
Over 50, it is recommended to pull back on intensive fa jin, extreme backbends, and holding extreme balance positions, or risk suffering the late life complications not uncommon for athletes at the highest level who sacrifice their bodies for their sports.
This is a good video of what a high-level, old school master is capable of in old age. He was trained by his father, who was extraordinarily strict. Take special note of some of the leg techniques, balance, footwork and focusing, and compare it to videos of most masters much younger.