We just delivered a multi-year project under Scrum (edit: point of clarification, we did not have a due date). You still have a guiding vision and some idea of the major milestones you need to reach, you still define what the next set of milestones are. You will want several sprints worth of work lined up ready to be more concretely planned. You just do concrete planning for the next sprint or so and work to minimize disruption of that sprint. Learnings being incorporated and plans updated as needed. Work that will yield more understanding should be prioritized.
Not sure where the idea of "only look one sprint into the future thing" came from.
"The whole idea that you can be agile while having delivery dates for things several months in advance is a nonsense. Agile is about doing what is important now, not doing what we thought was important a few months ago."
I agree with you - i dont think its worth trying to set a date a year out in stone. but you have to do exactly what you say. keep the trajectory in your mind and update it with new information. and and some point turn down the rate of change so you can get some cook time.
maybe I reacted too strongly - but I've certainly been in shops where I try to talk about overall project arc and am firmly told to keep my gaze fixed at exactly two weeks.
