Hey Cheeves! It's nice to no longer be the only newbie on the block. As for whether the relationship will last, as DMt and others have posted, here and elsewhere, the film ends on a positive and optimistic note, and that's where the girls are in my mind (and in my dreams which I'm
still having a month later!). Any conjecture about future happiness or unhappiness says more about the viewer than about the film. The film clearly intends to show that they have something solid. And they lived happily ever after? Unusual, but not unprecedented. And everything about them is unusual.
As for wishing the film were longer, it's never been a problem for me. If I were to add anything, it would be more character development of Agnes. More about her tastes in music and literature, etc. which we see only tantalizing glimpses of. Maybe Lukas put so much of himself into her that he felt he knew her completely and didn't need to elaborate. I love both girls, but if I could only choose one...I'm a sucker for those brown eyes.
Not that she'd have me of course.