I know many that never made it to their assignment. I knew one bethelite couple around 2003 that went to Gilead, but for some reason never finished. People around bethel gossiped and talked about them so much it bothered me. I mean, its a huge commitment to do what they are asking, I didn't see any shame in a reality check and changing your mind.
I can only think of one MTS graduate that made it more than 2 years in his assignment, and from what I hear he is struggling quite a bit.