I have reviewed different schools of thought on how often you should workout your abs. Some say daily. Others only 2-3 times a week.
Here is my opinion. If you exercise the abs intensely (and for more than 20-30 minutes), then limit workout frequency to 2-3 times per week. Otherwise, if 5-15 minute long workouts, you can safely engage daily.
Note: Make sure you exercise your lower back too. Proper balance between abdominal and lower back muscles is key to proper posture and overall wellness.