Yeah, this may sound a little gross, but if I know I won't be leaving the apt., I don't shower until I either start to smell or know I'll be leaving the apt. for work or what not. Now, that usually isn't more than 2 or 3 days, but for some who shower daily, I know that may sound disgusting. However, we never even reach our minimum water usage, so our bill is always $21/month. Always.