Yep, been stealing my wife's every since I got a job and a haircut. I use them to manage my cordage like you.
Though, I don't find it necessary to tie my shelter up. I usually roll it up and stuff it in my outter mesh pocket (it's a poncho trap though). I used to do my stakes like that, then I got worried about them poking stuff so now I have them in a tyvec envelope.
Good tip! They are definately more durable than rubber bands.