As far as I am aware, letting it discharge is only for calibration purposes (to ensure the battery gauge reads correctly).
I've been using my laptop battery for about three years with exactly this pattern, and what once lasted ~4 hours on a charge now lasts about 25 minutes.
If you let it sufficiently (not fully!) discharge at least once a month, I don't see why it would be particularly terrible for the battery, what am I missing?