The first time I purchased the product, I bought the 3.0-ml size, and it lasted more than 6 months, used about every other night. It did make my lashes longer and darker, so I was very happy. The second time, I bought the 4.5-ml size, and it was gone in about a month, although I kept it tightly capped, and used it 2 or 3 times a week. I thought it was a fluke, and purchased the 4.5-ml size again. The very first time I used it, I had to dig a bit to get much product on the brush, but I thought that might be the tube design, which kept you from getting too much. No such luck, again it was gone in a month, although I kept it tightly capped, and didn't even use it every night. Very disappointing, and now I don't know what to order.