Rinehart are the best portables I've used, I've been shooting the same 18-1 for at least three years now. I don't shoot it year round but for pre-season practice with broadheads it's held up great, much better than any others I've had. The Rinoblock is the same material only bigger and square, it would probably last a long time.
The sand pit or a big pile of rock free dirt is about as good as it gets although sand is tough on broadheads. I used to shoot into sand and kept a set of practice heads separate from my hunting heads. I'd shoot the hunters a few times and sharpen them up, then just shoot the "pit heads" for practice.