Chen Taijiquan

This will depend on what you want to archeive and your current physical state of health. If you are a beginner and recover from illness, moderating is important.
If you are after a healthy life style then it is commonly agreed amongst experts that 3-5 times per week is sufficient. You should be exercising for at least 20-60 minutes at 60-90% of age-specific maximal heartrate or 50-85% of VO2max (heart rate reserve). However, remember that your body needs time to repair. Your body won't rebuild until fater your training workout; no rest, no rebuild.

Here's an interesting tidbit. The biomechanics behind Chenjiagou Taijiquan's Fa Jing may be explained using plyometrics. Now, what is this plyometrics?