Hi I'm getting really confused with the semi permanent lashes. I have read that they last from 3/4 week up to 10/12 weeks, and have no idea what the difference is. All the salon adverts appear to be the single lashes applied to a single eyelash so are the same. Can anyone please give me any better idea of what to expect? Also does anyone do lower eyelashes, and if so are they ok? Thanks.