As already mentioned, most straight cases can be reloaded so many times that you don't need to worry about it. With pistol rounds I usually lose them before they are worn out. With 38 special, I'll bet I can reload a case more than 50 times if I don't bell it so much that I get premature neck splits. I'll admit I have never kept track of a single case to verify that, maybe one day when I am very bored.
With rifle cases that operate at much higher pressures, it depends much more on the chamber fit and what dies you use. With a loose fit in the chamber and full length resizing, you might only get three or four loads out of a case. With a tighter chamber, and maybe just neck sizing the case, it might last 10 or 20 loads. I have kept track of the number of loads for a few different rifle calibers, and they range from three for a 22 hornet with warm loads, to over 20 with a couple others. While I will push a 38 special case until it starts splitting, I try not to load a rifle case until it fails since the most likely failure is a head separation.