As I wrote in the FAQ, I decorated my own units.dat (units.lib in some implementations) with lots of stuff because I like easily editing units. (Nowadays I use Emacs Calc, but I still add a bunch of my own units, like the binary prefixes like mebi, gibi, etc.)

I suspect that a lot more can convert millilightseconds to miles out-of-the-box now at least in part because of the popularity of this story over the past 13 years.