Well, how long do you have to wear your retainers? Can't you just palate expand when you get them removed? I think that the palate expander should act as a retainer, but I am a very uninformed opinion.
The retainers are fixed so they will sit in permanently. What I don't understand is why I have to wear my removable retainer when I go to sleep, then what are the permanent retainers on the back of my incisors for?