Crepe myrtle will check (crack and split) like the dickens. It is a very hard wood once dry. The problem is it's moisture content. From observation, I would say that >50% of the green weight is water.
For most woods, I use wax on the end grain and let it cure for a year per inch of thickness. This will not work for Crepe Myrtle.
A local oldtimer, friend, carftsman, farmer, sawyer, and curmudgeon uses sparkleberry wood for farm tool handles (axes, hoes, shovels, ect...) Sparkleberry is very simmilar to Crepe Myrtle in the way that it drys and works.
He de-barks the wood and soaks it for several years in a handy petroleum substance (kerosene, deisel, whatever... don't use gasoline!) He has a 5' 1/2" long 3" diameter steel pipe that he uses as a tank. Even after such treatments, checks still happen.
I will say this. For all that time (waiting for the wood to cure) there are better woods out there. Don't expect too much from this type of wood.