The common rule of thumb seems to be: Less shiny = battle tested (hey, if it has bullet holes even better), Shiny = not gone even through pre-flight testing.
With less shiny I mean that it's old. Not that it is crummy qualitywise. Old code is not like wine. If it was crap then it will be crap now. Old code is like an old house. If it's well made and tended to, and built on solid principles it can last generations.
Extensible domain logic is something that generally does not age well. Old utility libraries with well defined interfaces, on the other hand, are invaluable in technical computing.
