Lun Hu Quan way
Standing in low mabu for 1 to 15 minutes.
Taijiquan way:
form - low stances very slow (example one Lao Jia Elu should take 20-30 minutes )
silk reeling - low stances (5-10-15 minutes without break)
ZZ - 30 minutes to 1 hour.
Chen Zhaokui
P.S. Warning your legs will soar, shake, have feeling of hot water streaming - it's normal:)