You might also examine your protective styling methods, as they may be contributing to the problem. For me, I found that when I used items like ponytail holders, metal combs and barettes, cotton scrunchies, bun donuts/socks and anything that was not silk or smooth plastic on my hair, I would experience breakage, especially in the back where I used most of these items to PS in tight buns.
Once I learned how to bun using only spin pins and to incorporate more protective styles like French braiding or side rolls with less tension into my PS reportoire, the breaking in the back dropped off dramatically, even though the amount of time I left my hair out in the back (which was not often anyway) did not change that much. When I do, I tend to follow the guidlines of one of the earlier posters, i.e., wear my hair out with more backless types of garments like sundresses or evening wear.
Also, carry a pin, clip or barette with you just in case you need to put up your hair during the course of the day. As live in the Southeast, the back of my neck gets sweaty pretty quickly when my hair is down, which gives those damp strands even more opportunity to snap off, so I rarely spend the entire day with my hair out anyway.
