What is the ruling on saying, "May Allah prolong your survival (or existence)" and "May your life be long"?

It is not appropriate to absolutely state "long life" [or "long staying"], because it can be good or bad, as the worst of people is he whose life is long and whose deeds are evil. However, it is permissible to say "May Allah prolong your life in His obedience" or "May your life be long in obedience."