So, multiple ways to clean out beer...
Easiest is to just drink it
Tried a few tonight, and thought I would report on the results.
These included a 2006 Lagunitas Gnarlywine, a 2006 Troegs Mad Elf, and a 2007 Deschutes The Abyss.
First, none jumped out of the bottle and tried to kill me. No scary smells, no chunky pours, a universal lack of carbonation -- but some caveats on that point.
Tried the Mad Elf first. 12 oz. bottle, standard cap. No carbonation at all. 11% ABV, was originally quite hoppy when fresh. Hops were gone, cherry flavor still present, some oxidation (cardboard flavor). Not bad at all, but clearly past it's prime.
Tried the Gnarlywine next. 22 oz. bottle, standard cap. Slight hint of carbonation when opened, but still a very flat pour. Hops were gone, decent flavor, came across as more of an old ale.
Finally, opened the Deschutes. 22 oz. bottle, standard cap, but waxed. More than a hint of carbonation, and some actual bubbles when poured. I don't recall if this was particularly hoppy back in the day, but, if so, that had dropped out. Silky smooth, with flavors of coffee and chocolate. Enjoyed this one, and it had held up much better than the others.
Will try more, and post results. If anyone else has "vintage" beers, and would like to contribute, feel free.