I purchased a Gallon of tea tree shampoo in 2005, and today I just finished it. I purchased a smaller amount initially, liked it, and then purchased the gallon, and would fill up the smaller bottle as needed. I have short hair, but shower/use it every day. I am suprised it lasted so long, but I dont regret the decision of buying the gallon. I would say be absolutely sure you like a shampoo before you buy a gallon of it - its a long term relationship...