I have an end-grain cutting board of "Chinese Ironwood" like this one from the Wok Shop. I've used it heavily for the last 16 years, and it shows very little sign of wear.
However, I have to sharpen my knives more often than it feels like I ought to after use with an end grain board; like every 3 uses to maintain a keen edge. This has brought me to wondering: what exactly is "ironwood" usually, and is it one of those woods that wears down knives faster, like teak or bamboo?
Based on its density when compared to other hardwoods, I would say it would (see here). Also, having used one (I had a nice circular board, when I lived in China actually) and I noticed it as well. Just like you say, in order to keep a good edge on my knives I was sharpening more often than I was accustomed to with my endgrain cutting board (made myself out of maple and walnut) as well as my bamboo one.