I bought my bike new about three years ago. Since then I've had issues with spokes breaking and needing to be replaced, probably around ten times. Presumably the spokes weren't up to snuff. I've always just replaced the spokes as they break without changing out the spoke nut, then re-trued the wheel. The replacement spokes have largely been fine.
I tried truing my wheel recently and found that as I tightened the spoke nuts, a high percentage of them rounded off, or in some cases flaked apart, and had to be either removed with grip pliers, or taken out after cutting the spoke. It seems the nuts are brass. I started replacing them with steel ones, and that's been better, but I'm still rounding some of them as I try to true the wheel. My spoke wrench is a Park Tool SW-7.2, which I'd think should be adequate.
What's going wrong here? Are both batches of spoke nuts bad? Is my wrench not suitable? Am I way overtightening the nuts? I haven't seen any discussion of this problem with a quick search, so evidently I'm doing something really abnormal.