If your last job was way too easy, to the point where you were slacking off, and you were involved in training your replacement, what was that like?
Did the new person's time seem filled enough as they learned their new duties, letting you escape before they, and possibly your manager, realized that you'd been slacking? Did you hint to your replacement that the job would be pretty easy once they learned their way around, or did it seem like it could take years for them to master the position, so you said nothing? Did you even care about what people thought after you left? (I guess I do, I like my workplace and the people here, and want to leave on good terms.)
I've had my job for many years and am the only one supporting my group in this role. While I've taken on a number of duties over the years, expanding my role into areas that in other groups are staffed by additional people, I've also learned how to slack off and still get my work done on schedule. It's largely a matter of knowing which projects are likely to be delayed or cancelled, and which tasks can be put off because the details will likely change later, required rework at my end.
I expect to cut the cord next year, and am looking for input as I consider the various aspects of my exit strategy.