Permanent retainer experience?

Hi, my dentist said that apart from a removable retainer, I will need to have a permanent retainer on my upper row of teeth. This is cause without it, my my two gaps which we have just managed to close will open up. With that I have a few questions:

  1. Do they easily break?
  2. I imagine flossing will be difficult. How do you suggest I clean between my teeth?
  3. Will I need them on forever? Would my removable retainer suffice after several months?
  4. How is the pain? Will I forget it’s even there after some time?