in one long evening, with enough patience, you can comb them out.
mine were 8 months, pretty mature, locked to the roots (never had the loose roots problem). bleached, dyed, fried. i didn't use conditioner precomb. so i'm pretty sure anyone who has pretty managable hair may be able to get away with it.
never thought i'd see them go, because i went into it pretty spiritually and watched; as they dreaded i found 'me' and i found beauty and i fell in love with somebody truly amazing. but, a few months ago, i dreamt i combed them out. every dream after, i had straight hair. and i think i'd really learned from them, and i need to try straight hair again.
this wasn't my first set and i'm sure it's not my last.
i'm rather shocked that my chin length hair is now shoulderblade length.