I hacked one of our Hebes back hard. At the time, I thought it was a Buddleia, so you can imagine the butchering it had! It bounced back really well, so I suppose it depends on what type you have. But then, if you're planning on taking cuttings and getting rid of the parent plant, it's probably worth the risk..
I've just stuck 10" long prunings in the ground and left them, and had about 80% successful rooting. :)