Kukicha
I have used kukicha tea for many years. It does NOT become bitter with longer "steeping". I make it by the gallon, simmer it for 20 minutes with a small piece of cinnamon stick, 3 de-headed cloves and about a half teaspoon of cardamom seeds. I then cool it and put it in glass jars with the "grounds" and spices remaining. It lasts for weeks in the refrigerator and is delicious!