I have yet to use chamomile but I would think that you would want to add it at flameout as it can get a bit bitter if boiled. plus you would lose alot of those delicate floral/honey notes that are so nice.
I agree with this. Any tea or any tisane (which is technically what chamomile is) should be steeped and never boiled, for those very reasons.
Actual 'tea' shouldn't ever steep for more than 3-5 minutes (less for green tea...preferably not more than 3 min); with herbal tisanes like chamomile, the timings can vary somewhat, but you still don't want to overdo it, lest some of the harsher notes emerge.