On 13 Apr 2015, Dan Espen wrote in rec.gardens:

John McGaw writes:

Is it too late now to think about dividing it? Will I simply
cause troubles for the original plant(s) by dividing so late?

No problem dividing now.

I've done so, spring, summer, fall.
I don't think the plant cares.

Those things are almost unkillable. I wouldn't hesitate, either.