I've been wearing SPF 70 ( ) since the beginning of the summer, but I've still got lines! I actually love my wrist line. Otherwise, I switch between different length shorts to break up the thigh line. My arms don't really have a line because my team jersey is very thin, so it lets in enough sun that my upper body tan lines are sportsbra and bib-shaped.

You could always look around for a bottle-tan that somewhat matches your natural color and apply it to your white areas.