We've not talked nails for a while. I have discovered CND Vinylux which lasts for a week with no chipping. And it really does. You don't need a base coat, you paint on two coats of the polish and the special top coat and bob is your uncle.
I had them done at the salon across the road from me and was so impressed that I invested in some colours myself. It's exactly the same as normal nail varnish in terms of application and it comes off with regular nail varnish remover. I don't know how it works but it does.
I bought these three colours from this site and am now cooling my heels before I start another obsession of buying 500 new colours.
Here are my nails in the blue which is exactly the same as the wondrous YSL blue. Disclaimer: these are done by the beauty therapist, not me. I am not that good.
If you find your nail varnish always chips no matter what you do, then give this a try.