I've found out the hard way that the only socks that don't develop holes in a few months are ones with nylon. Not even silk or bamboo work. Almost all of DP's newer socks have holes in them, because I've been making him nice soft socks with pure merino. I should have realized that they'd never last, but I let myself be fooled.
The good thing is that the socks I'm currently making for him are in a wool/nylon blend, so they should stand up to wear. The bad thing is that, like almost all his socks, they are 9 stitches and 12 rows to the inch, so they won't be done anytime soon. I have to get him hooked on STR I think, because the only holes those socks get are from severe injury - catching them on a nail, accidentally cutting them with a scissors. Blargh!
I might have to whip up a thicker pair for him in between other projects, just to take the edge off, you understand :)