I, for one, reckon that being tickled to death would be something to avoid. It is preferable I suppose to being burned to death or buried alive, but it would still be a bad thing. Yet, it is often said that we would be tickled to death in connotations that imply that such a state of affairs would be welcomed. "I'd be tickled to death if you could help with conference" means that such help is welcomed not that the speaker supposes that such help would be like being tickled until dead.
I'm not sure that it is even possible to tickle a person to death. I surmise that at some point the nerve endings that send the tickle sensation to the brain would cease to fire and that continued contact would no longer tickle long before death. Moreover, tickling does not, as far as I can tell, cause any actual injury to the tickled person.
If it were possible to tickle someone to death, I imagine that there would be warnings about tickling babies.