The other point I would make
@The Insomniac is that with regards to how many years Luke has left in FG (which I assume was your main point?), he has had very few injuries and no major injuries over his career (to my knowledge) which offers 2 considerable advantages...
1. His durability - particularly to a squad with multiple recurring injuries in a rather fragile spine and backline (DCE excepted)
2. His career length - similar to Chez, he seems to still be enjoying his footy and his lack of injuries and desire to play more finals may see him play on for a longer period of time than your average NRL player...
Just my thoughts...