Soslychic, I'm the weirdo who wears braids 24/7 and my hair gets messy only when I wash it, but not so badly that I can't wear it that way to work. Just messy enough for me, since I know how *I* braid and how I can make it look. But because I redo the braids often, especially the areas that show (eg, where I have a part) I can easily disguise the mess until I get to those braids. Or, I will sometimes wear my hair in two (out) French braids on either side of my head meeting in the back for a day, (I do this when my hair is damp and after applying L'Oreal Anti Frizz Serum). Then when my hair is dry I do a braid-out and wear a wavy style for a few days coz the waves work as a great disguise. Sometimes I'll don a hat or headdress if the bases look really bad, until I get a chance to redo the outer more visible braids.
Tying a scarf when you go to bed might help keep them neat. I'll also share with you what I've been doing before going to bed lately. I have been bending and letting my head hang down so my braids are hanging towards the floor, then wrapping Saran wrap from the base all the way to my ends - kinda like I'm wrapping a mummy. (By hanging my head down I make sure they stay more or less straight - although spritzing with water in the morning would get rid of any kinks.) The main reason I do this is because I have been spraying S-Curl to my hair ends (not the extensions) at night and thought this might help it all get absorbed into the hair in the night. Also, I am obsessed with sleeping in plastic caps so I guess I get the same "benefit" (if any) this way. In the morning my braids have been looking pretty OK and very moisturized. BTW, I only use Dew for my braids, and only in the morning. But after a night of Saran wrap, my hair feels as if I had sprayed S-Curl all through it the night before.