They did but unfortunately they seem to reply to the wrong email because their answer is nothing close to my question. I gave up and just try to look for information from the group.
This is quite vague tbh because I apply via e-visa so they only require us to fill in an "Expected" date of arrival and departure only. You could easily fill in a unreal date because it's an "expected date" only, it's not a sure thing. If later on they ask for booking confirmation/receipt, you can just book a hotel/airbnb that allows you to cancel.
I think I kinda understand your question, pls ignore if I'm wrong. It's true that the visa is valid for 5 years, but from what I apply which is Hanoi, Viet Nam embassy, you can only apply maximum 3 months before your estimated arrival date.