No offense intended, but this is like asking how many times you should wipe your ass. The answer is:
It depends. Use a little common sense.
Whom exactly are you concerned about becoming suspicious? Do you have a lot of FC-mates or friends online whom might find it odd that you’ve run Stone Vigil for hours on end? Perhaps you should wait for them to go offline before doing a bunch of runs.
My recommendation: NEVER let Miqobot run unattended, ever. The only stories of people getting banned that you see on these forums are from users who let Miqobot run unattended for a very long time. Break up your run times and always be present/near the keyboard so you can respond to anyone that messages you.