I've been given a lower essix and will be given an upper essix to wear for 3 months 24/7.
This is followed by a Hawley (not sure if it will be top or bottom or both) for night time wear for a year.
Followed by this, I will be getting a bonded retainer for the lowers only (though this might be the same time as I get my Hawleys, not sure yet).
I have been pretty good about wearing my retainer, the longest I had them out for was an unavoidable 4 hours once, and it did feel tight when I put them back in but not too tight. My ortho also told me he thinks my teeth will be pretty stable

so I can stop the night time wear completely in a couple of years! (although I think I will probably keep a check on them every now and again with the retainer anyway, just in case!)
As for the bonded retainer, they are semi-permanent, as Merytan said, if necessary, they can be replaced. I think the life of the bonded retainer is also affected by how well you keep it (cleaning etc)..