I've had them relaxed, in transition and natural. The only problem I really had was when my hair was in transition, the two textures + the knots I had to comb out was a terrible set back. As a natural I will admit that they do not last as long as they did when my hair was relaxed (especially after you wash them), but it is a really great protective style, and I have retained every inch that I have grown!
Whether they last or not depends on how long you want them in your hair. I generally try to keep my twists in for 2 months, but they start looking a little rough after 4 weeks.