The best and worst part of a futon is how few parts it has. Its nice that there are only a couple when you are putting it together. But if something breaks like the frame, which is the biggest part, you have no choice but to replace it.
I have a futon which has a huge bend in the middle. It is really uncomfortable to sleep or sit on. I can't just get a new rod or something, I have to replace the whole frame which means the whole futon. What a pain in the neck.