I used to change my colour so much that I didn't actually care if my manis only lasted a week. Now that I have a toddler and a slight case of pregnancy induced narcolepsy I want to paint them once and leave it on for a few months (joking...kinda) I love cheap nailpolish. I can't commit to one colour for long enough to invest $30 in a bottle, even though I know it is better for my nails and it will last longer.
My way around this is to spend good money on an OPI Start to Finish top and bottom coat and keep using my stupidly huge collection of chemist colours. It's worth the $22 ladies.