They work (cr-mo) but are definitely a consumable. My 17 split after about a year of moderate use. Haven't tried to warranty it. Went to a set of koken sleeved wheel sockets and Sunex 284915 which are much deeper (for long lug studs). The koken are expensive but I expect to last much longer and the astro are necessary for my race car (sunex got a lot of use on there).
I think as long as you go in knowing the thin wall stuff is going to eventually split (ie, might get two if losing it would be a problem productivity-wise), you'll be fine. Given that, this is one case where I think confirming warranty coverage and using ease-of-warranty in your purchase decision makes sense.
ahm