if you mean Luka Megurine as in the vocaloid, her character is supposed to be 20 years old. However, her software was released on Jan. 30. 2009, so the software would be a little over 3 years.
MEIKO's package was released in late 2003. So the package itself has been out for around 7 years, concidering now is the end of 2010. If you're asking for the vocal age, I would assume over 20.