I think my favorite part about Wall-E, among all my other favorite parts in that movie, is that Wall-E is apparently a singular trash reclamation drone, that somehow survived so long beyond the end of human civilization & all the other Wall-Es, that he has in some way developed to a point nearing artificial intelligence, BUT he's still actively following his same exact trash reclamation drone program. Which means, that it might not be a program anymore. He might have become self aware enough to know he was a drone with a program, & after having considered his solidarity, realized that not only did he have nothing else of value better to do besides continue it, he probably also made the personal choice that it was still the right thing to do. Basically, without it being spoken of in the movie itself, Wall-E isn't still cleaning up Earth because he's programmed to anymore. He's doing it because he wants to.