"When you load them 'till they split, do you notice when you shoot it? Or just after you collected your empties? In other words, has old brass splitting during firing ever caused a problem in your firearm? Enough of a problem that you worry about safety?"
For me anyway, most splits occur during loading, not firing but such splits are not usually any problem. (I say "usually" because I never say "never" and "always" when discussing reloading, some "expert" will always have a story about his friends neighbor who had a great uncle who knew a guy who heard of a different experience!) Hand gun cases typically split in either the mouth or body, not the head, so the pressure is still contained well and produces no hazard to the shooter or his weapon.
Many people limit reloads to five. I suspect that's because some magazine writers have said that so many times it has become conventional "wisdom". It is a safe enough practice because it is so conservative that people toss perfectly good cases before it's time.
Five reloads is a reasonable limit for hot loaded rifle brass and when the loader fails to adjust his FL sizer to match his rifle's chamber. But, the limit of five has little application to handguns, the pressures in pistols are far lower, even in "hot" loads. And hot loads are a dumb idea in pistols.
Keep your brass segragated by number of reloads. When one splits, toss the rest. If your chamber is tight it will last a long time, if the chamber is large and your sizer is small and you over crimp a little to much, the cases will split much sooner.
Some cases have soft, longer lasting brass, some will be harder and it will split sooner.
There is NO way to predict how long any of it will actually last but it will likely be something like ten or more. Maybe much more.
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