I remember finding that work by Moebius fascinating in its own way, in large part because of that very quality. I also had heard that from Toriyama-sensei, who has always been very honest about his motives in doing comics; in one interview, he was engaged about his sweeping natural landscapes and his tendency to set the fights in such places in nature, removed from the urban sprawl. He replied that he just hated drawing cities and buildings, so he avoided it whenever possible!
Personally, regarding the original question here, I never have an ending concretely planned for a series. Things change, circumstances change, you'll get to know the characters and circumstances, and to be quite honest, unless it's a very short story and you're writing it for a very specific point, you probably won't be well-served by too rigid a concept of the ending. Of course, you can have a general idea of how you'd like it to end without being too intractably written in stone, and that's what most people who plan that far will do, as @thomasfallaeriksen pointed out with his own approach.
When I plan out individual stories and chapters, of course, I tend to have somewhere I want them to end up, but I'm not afraid to change that depending on how it goes during the chapter, in little or large ways. Sometimes the planned ending doesn't work out at all, and it has to be changed significantly. But I'd rather go with what feels right than to stick with my original idea and feel uncomfortable with how it turns out. So many things change, inevitably and invariably, during the process of writing and creating. Sometimes even the visual impact alone sways how a story will go.
I usually have some idea of a desired resolution, several points along the way I want to illustrate, and then I work with those things in development. But I wouldn't want to leash myself to what I think is a good idea before I really get to know the story, the circumstances, the characters, and quite importantly -- especially in indefinitely ongoing series -- the readers. A writer's approach is very important here, and it can make the difference between readers feeling appreciated (which does not equate to pandering, n.b.) and readers feeling resented, or like the writing exists to spite them. Sometimes being utterly disconnected from readers, for the sake of sticking to a plot developed long earlier, can be a harmful thing.
So there are many considerations. "The best laid plans" and so forth! It's just not a simple question with a simple answer. Even if you plan out in detail, you're inevitably going to have to change something, sooner or later, so I think it's best to try and be flexible in most cases.
