After using OPI Nail Envy on my own natural nails for over a year and having great results I have decided to give Toughen Up a try. There are no instructions on how often to use TU and I have just spent ages looking over previous threads on this subject and am still not sure. Should I apply one coat to natural nails then varnish, then top coat and re apply every 2-3 days and then remove after a week and start again(all products are creative by the way) Should I use it forever just in case nails weaken if I stop, what does everyone think. Annie x