I planned on keeping all of mine, because they were seemingly not causing me any problems and that's that an unnecessary expense/hassle to remove otherwise fine but worthless extra teeth.
Then one started erupting, and the Army noticed it during an exam. Since it was only partially erupted, it could become infected since it's difficult to clean and whatnot. So they marked it as "this must go" and the Army pestered me (in the Reserves, we only have to somewhat listen to them) and finally command set a deadline.
No way in hell was I going to have an Army dentist touch my mouth outside of a screening/exam, so I found a dentist who agreed and got me an oral surgeon.
Turns out that partially erupted, but still impacted, wisdom tooth was actually scraping away at the next molar, causing bone loss (which I am promised is reversible). So, it really needed to go.
Problem is, I'm a wimp and would not agree to extraction of that one without being knocked out. I couldn't get knocked out (general anesthesia) and have only one tooth extracted unless the doc agreed (he did), but regardless, insurance would not cover it. It cost me basically the same to have all four yanked with anesthesia (with insurance) as it would have for 1 tooth and anesthesia.
That was a little more than two months ago. I'm 25.
It wasn't too bad of an experience. I took long to heal, and I still have a pocket where the one problem tooth was (that one was the worst, that side of my face was the most swollen). But already being in misery plus the bonus of vicodin made it easy to quit tobacco (snus), so... it was sort of a win-win in the end.