Keurig Single Cup Coffee Makers are a recent fad. Customers often ask me about making tea in their machine. I do not support their use in tea making. Teas require steeping. The chart below is a water temperature and time guide for tea steeping. This chart addresses true teas: white, green, oolong, etc., it does not include herbal teas. For herbal teas, light leafy herbs require more tea and less steep time, roots and seeds require less herb and more steep time. The chart also tells how many times you can infuse (reuse) the same tea. Note that when brewing a caffeinated tea you will get most of the caffeine from your tea in the first cup (up to 80%); each time you re-steep, you will have less and less caffeine.
This chart came from Wikipedia, the free online encyclopedia; it is a great reference tool. This link will take you to their post on tea.