When it's time to drop the status of "assignee" and make the transition to a local employee in the host country, you "localize"! Localizations are primed to increase, so it's important to evaluate your strategy now.
Over the past few years we have seen a steady decrease in the number of long term assignments and many mobility professionals are expecting this to continue.
One of the questions I help companies resolve with greater frequency these days concerns intra-regional moves and the advantages (and disadvantages) they offer over traditional expatriate moves.