A self-winding watch needs to be worn for hours each day to not run out of power. A manual-wind watch will be a better choice for a night-only mechanical watch.
That used to be the case, but a lot has happened in the last few years. Most of the time you'll be able to move a large Rails application to JRuby without any changes at all, except adding a Warbler config for deployment.
We use JRuby for a one of our backend applications in production, but we develop them with plain MRI Ruby. Only real problem we've run in to was some of our badly performing (badly written) parsing code that ran even worse under JRuby.
I wonder how these 1980's results relate to object oriented code and other things that have happened since then. Even 25 LOC would be a huge method in Smalltalk-style OO for example.
Other than OO, we also have much better tools for navigating code now. That may have changed how we approach and understand unknown code.
A few of my old colleagues bought the code from our bankrupt employer and made a second attempt at creating a business with it. They did better than the original owners, but not much.
In all other cases I've come into contact with the code just dies. Open sourcing would be nice, but that's obviously not a priority in a bankrupcy.