The full sized bottle for this brow gel (tint? mascara?) is super tiny, almost sample-size tiny. I've been using it nearly every day for 2 months and I think it's nearing the end of its life. So I'd say 3-4 months for this product, which is not that long for the cost.
It does work really, really well and gives a quick, natural, stay-in-place brow. I like to use it after I fill in with a pencil, as this product doesn't really fill in sparse spots so much as enhance what you already have.
Honestly, I wish I didn't like it so much because it's more expensive than I normally pay for brow products.