I got into guns pretty much around the time of Sandy Hook. It suuuuuucked. I cant see how anyone who went through that can look down on someone as being a hoarder. (not aimed @ xtry)I have far more mags loaded with ammo than 1,200rds. Obviously I can't carry 56 mags, but it's enough to load out two fire teams without handling loose ammo. I have three family members in my house with their own ARs, that can use them effectively.
My idea of having enough is think of a reasonable situation that could occur, and then have more than that.
The main differences here are what each person views as "reasonable". There are so many factors beyond "needing" ammo for self defense that make it prudent to purchase more than you would typically use such as:
1) Ammo prices don't go down
2) Ammo shortages happen, possibly restricting how you train
3) Unforseen events happen and you can't plan after the fact.
I enjoyed going through the post Sandy Hook shit show and never worrying about even rationing my ammo or training schedule, let alone concerned how I was going to find ammo at all.
As someone else said, it really is like toilet paper. Youre always going to be using it (unless you for whatever reason see yourself getting bored with guns and giving them up for something else), if the price is right and you have the means, its asinine to buy just one and use it until its almost gone and then look for another box/case.