It's hard to talk about "The Simpsons" these days without having an existential crisis over the age of the characters. If Bart had aged normally, he'd be 46 right now. Homer should be deep into his 70s, and even Maggie should be a fully-grown 37-year old. Even the news of a second "Simpsons" movie coming out in 2027, which should've been a wholly happy affair, came with the sobering reminder that we are now further away from the first movie than the first movie was from the show's 1989 premiere. Time keeps on slipping and we're all going to die one day, though rest assured Lisa will still be 8 years old when that day comes.
The result of the characters' immortality is that the show has to work with a floating timeline rather than the realistic timeline a live-action sitcom would opera