[X] Let Zangetsu stay released
[X] Admit you have it if asked
Here's the thing: Remember that comment Yachiru gave in literally the update before this one? About how or blade is 'Proud?' Which does, indeed, fit Zangetsu to a T. She also equates it with her own blade/herself (Because Yachiru is weird).
Zangetsu wants to show off. That's why he's straining against the normal shape of his unreleased state. After all, Zangetsu is Ichigo's instincts, his will to fight, battle, win and survive. He is the epitome of the thing that makes Ichigo a fighter, and like any being comprised of battle honed instincts, he hates being restrained. In the grand scheme of things, letting him stay in a released state is a step towards accepting Zangetsu as a part of ourselves. Forcing him to stay unreleased, retraining him, is like symbolically restraining a part of ourselves.
Some people lend themselves towards that. But Ichigo? He might not say much, and be a bit humble, but when it comes down to it, he is a proud, stubborn motherfucker. He'd buck just as much as Zangetsu at the thought of being kept from doing something he thought was important.