To be fair, instances of lasting change through episodes were rare, usually necessitated by staffing/pay disputes (e.g. Maggie Roswell, who voiced Maude, leaving after wanting money for travel and not getting it, thus Maude being killed off) or death of the voice actor (e.g. Marcia Wallace, who played Edna Krabappel, among others).

And I do actually remember the amazement in the community when she stayed dead, rather than springing back to life as though it had never happened in the next episode.