Ballast Resistor

I've had my '66 Barracuda for a loooong time. About 10 years ago I put in a 72 360 engine with the orange box electronic ignition. I have an older style 2 blade (single coil) ballast resistor that has been on the firewall for I don't know how long.
I heard long ago they were a weak link, so I kept a spare in my glove box. The other day I was sitting at a red light & the engine died. I thought maybe I had run out of gas, but it turned out to be the ballast resistor was fried.
Thankfully, In minutes I was able to switch in the new spare that had been gathering dust in my glove box. I'm just curious, is there anything that I should check that may have caused the resistor failure...or do they give out now and then....well....just because?