Three years on a stone
Of course we're beginners all our lives. But that's kind of semantics. Although we continue to learn eagerly and humbly, we do progress.
Normally, when the student is allowed to put on a hakama he or she is expected to have reached some kind of intermediary level - being able to practice with reasonable vigor and focus, and so on.
I think of the old proverb: Even on a stone, three years.
Even if it's something as simple as sitting down on a stone, it takes three years to learn.
But after three years, you've got it. You can sit on a stone. After ten years you know it even better, and after thirty you are surely a master of it - but anyway, after three years you have the basic skill.
I think there is a three year thing in aikido: You certainly don't master aikido at that point, but you have become aware of how far aikido can take you, what you can reach by it, in the big perspective. That's the first "satori" of one's aikido path: seeing how far it can lead.
When it comes to my students, I expect them to have that kind of insight after three years of training. And I expect them to reconsider whether they should continue to practice at my dojo, or move on. If they make the decision to leave earlier than that, I am sure that they have not yet grasped what they might be missing - or not. If they remain after three years, I am honored.
They are still students at the dojo, but with another awareness, and therefore I try to be more receptive to their needs as they see them.