Is this a trick question?
- Once, because then it's different ammo.
Seriously, if the question is how many times a brass case can be reloaded, the answer is
Warm loads, fully resized, fired in a SMLE, maybe as few as 3 reloads. Hirtenberger 7.62x51 brass in my M14, about 6 reloads, My father's 7mmRemMag has some cases he's reloaded 35 times, and benchrest guys often get more than 100 reloads out of a piece of brass.
The chief variable is how much working the brass gets.
- Fired in a loose chamber, with a generous neck, in an action with rear locking lugs, then squeezed back to minimum SAAMI specs, means the brass is getting an awful lot of working. It's going to stretch like crazy. 3 reloads and you're flirting with a head separation.
- The same case fired in a super tight chamber, in an action with properly lapped front locking lugs, and in reloading only the neck gets squeezed 0.003" just enough to hold the new bullet, this case will last a long time.
Depending on the action/chamber design, the ammo's pressure can be a significant factor in case life; but it's not written in stone. Have a look over at 6mmBR.com, these guys get over 2800 fps with the 107 grn MK out of the little case. That's just a couple ticks slower than the .243 The pressures are pretty darn high.
visually inspect each case after cleaning. Handguns, look for case splits/cracks along the case body and at the mouth.
Rifles, look for a ring near the base.
I inspect cases visually and audibly. Take a hand full of brass in the same caliber and pour it back and forth between hands. There shoud be a uniform tone to the brass clinking off each other. A cracked case will have a flat tone. I put half in each hand and jingle them. Whichever hand has the uniform tone gets dumped in the "good" can. Split the other hand full into two hands and repeat til I get to the bad case. It take s some practive to get your ear calibrated but is quick and effective.