Having enough extra magazines is only part of the question for me. The other and maybe most important part is organizing and storing them where I can find them when I want to go shooting.

I like to use these nylon storage pouches from MidwayUSA. The have six individual pouches that will hold either 6 double stack or twelve single stack (1911) magazines. As they come in different colors so I use a different color for each different type of pistol. Best of all is they are inexpensive at only $9.99 each on sale. So for my full-size pistols I have at least two pouches each which means 12 magazines.