Can one drink too much tea?

I've observed lately that I seem to be drinking a lot more tea than before and was wondering if there was a maximum amount of tea that one should drink any given day. I tend to drink decaf tea, so it can't really be caffeine that I'm getting hooked on. (Currently I alternate between Tetley decaffeinated orange pekoe and a selection of Celestial Seasonings herbal teas also lacking in caffeine). As well, when I drink tea I don't add any sugar or the like to it so it doesn't seem to be sugar that's driving me to drink tea.