For South African Jews, "I wish you long life!" is certainly the standard
greeting at a funeral and a shiva house, not only to the direct mourners,
but also between other attendees. Outside SA, it immediately identifies the
person who uses the expression as a South African Jew. For those who use it,
it has a great comforting effect.
As one who frequently officiates at Shiva houses, I use the expression all
the time, and always explain its cultural significance to non South Africans
- who also find it a source of solace.