I'm not sure if this was covered somewhere in the novels or this forum, but from what I recall... Zhang Jun Bao separated from Shaolin at age 16 or so and started cultivating with taoist scriptures for some years. Then of course, he founded Wu Dang receiving countless pupils and grand pupils.
I remember when Zhang Cui San came back from the Ice Fire Island, they made it just in time for Zhang San Feng's 100th birthday. At the time I'd say Zhang Cui San was no more than 40? That's a sixty year difference in age.
When did Zhang San Feng found the Wu Dang school and start taking in students?