[Casey6]

But there is a little bit of a difference from how they were Hollowfication and how Ichigo was Hollowfied.

Aizen made them into hollow which seems like he used a different method which seems like they would not have able to change back to their normal form.

When Urahara changed Ichigo, Ichigo was able to turn into the shinigami by breaking off the mask.

So to me it is natural the others can tap into and hold onto their hollow form longer than Ichigo, because they were never intended for them to change back to a shinigami.