No, you can't have a long term contract. That would confuse the audience.
I know I'm supposed to be afraid that the Hirogen dump their victims in giant vats of external stomach acid, but really it all just bores me.
JANEWAY: You see Doctor, if you don't quit complaining about your mobile emitter being damaged, we'll transport Neelix's lungs away again.
DOCTOR: I'll be good.
Heh heh. They'll pretend to like anything if I tell them it's a delicacy. Even Talaxian hog feces.
Leave me alone. I just found out I'm going to be fat in 15 years.