Yeah, the long hair showed him maturing and seemed more Sage-like. Now he's got the basic-protagonist haircut again.
Probably just easier to draw...
Fr they always chopping off the long haired baddies
The author wanted the long hair, and actually enjoyed drawing it, but their editors didn't agree. Since hair is not that important to the main story, I think the author just went along with what their editors wanted, mostly to avoid clashing with them.
The editors can suck my ass because he looked great with long hair. With short hair he looks like any random dude you can find in a gas station on a Wednesday.
Disappointing that they cut his hair