I had a permanent retainer on the bottom for at least 10 years until I bent it while eating a frozen snickers bar. My teeth started to move right away with the retainer bent of course so the ortho put another permanent retainer in which laster a few more years until I did the exact same thing. He then took it out as long as I promised to come in if my teeth started to move. Mine were fine until I got my wisdom teeth taken out, then my front teeth started to look like they were starting to get uneven so I went in (which was at least a year after my wisdom teeth were taken out) and was fitted for a normal retainer now. I have been going for over 2 years now with the normal retainer trying to get them back to where they are suposse to be - of course to me they have looked fine for a long time I know what you mean about not wearing your retainer for a few days - I am bad about wearing it and it is so tight when I have missed a few days.