The main thing is that the threads are loaded in tension and compression with very, very little bending. Loaded that way, pretty much any threaded steel rod in that size range will live forever with the loads coming through there.The BMR rear arms don't have a threaded link like the ones from FTBR and Steeda and so on. It's a billet aluminum part with a double-threaded sleeve that does the adjustment. Overall, it's a lot stronger than the "turnbuckle" style adjusters, but in the end it still comes down to the strength of the threaded steel rod on the spherical rod-end.
These and the SPC are both good designs for a much easier adjustment than a stock link in the subframe slot.