Use distilled water to help dissolve down the heavy deposits that build up from time to time.
I still use vinegar or lemon juice to get the heavy stuff out, but sometimes just using distilled in our heavy water area still acts as if I used the vinegar/lemon juice - it cuts up all but the most heavily baked on stuff. So I switch back and forth between the two to avoid etching the metal in my iron/ teapot or the plastic in my cups.