I shoot broadheads into compressed bales. Out of my 45# hybrid, my hesds only penetrate about the depth of the head. They are a little hard to remove (I brace my knee against the bail, and it takes a good pull to get 'em out), but I like to think that speaks of their durability.
Had the target for less than a year, so don't know the longevity yet. I have a cover with good overhang on mine, and I use only one bale. Have a dirt bank behind it, so I'm not really worried - unless I hit the wood base it sits on!