After a spoke breaks, do you finish the ride that way, or do you walk/drive your bike home, pull the wheel off, and take it into the shop? If you ride on it, minus the busted spoke, that's putting an awful lot of strain on the other spokes, which is why they're dying. It's kind of like dominoes.

Also, truing and tensioning a wheel are different things. And some spokes are stronger than others.