If the spirit is strong willed it will p off the spirit bad and it will come back and you will cop it worse.
 do you mean that it will make the spirit more angry and prone to inflict more damage than it did before the smudging? [/edit]
Depends who you are up against.Saging will make the spirit go away, some will go away for good, some will come back. Just depends on the temperment of the spirit. If you are up against a very active & angry spirit, there is the possibility that they will come back with a vengence.
Most earthbounds arent like this but some are.
You cant burn sage continually in your home.