The longest I let tea steep is 5 minutes. Most of my teas I stop between 2-3 minutes. I find it is way too bitter for me if I let it go any longer. Then again, I also use 175 degree water for my green and white teas. That is what is recommened because they are a bit more delicate and steeping them at a higher temperature essentially over cooks them making them bitter.
I can steeping herbals for a longer period of time, you are able to extract more of the flavors that way and since there is seldom any tea in an herbal there is no real risk to steeping them a long time.
You can find whole Chamomile at Tea Gschwendner if you cannot find it around you. I would say I buy about 75% of my teas from them. They sell a Rooibos Lemon that I love when I am sick. The lemon is soothing on the throat and the rooibos gets me a ton of extra anti oxidants.
http://shop.tgtea.com/store/product/...e-Blossom-Tea/