So the topic here is VARIETY...
I have hanguns in .22LR, 9mm luger, .357mag, and .45ACP.
I have long guns in .22LR, .22WMR, .243, .30-30, .44mag, and 20 guage shotgun.
At what point do you say enough? Is there and advantage to keeping it limited to fewer calibers?
There is a point when the advantages of economies of scale and commonality of parts starts starts to decelerate. That is to say, having 3 guns each in 4 calibers isn't that much less of an advantage than having 4 guns each in only 3 calibers.
At some point, there has to be a determination made whether the bargain you are able to get or the preference you have or the better suitability of a niche caliber outweighs the benefits of limiting your stockpile.
For me, I already have rifles in 22LR, 5.56x45, 7.62x39, .308, and 7.62x54R. More than one of each (in my own defense, many are milsurp, used, or otherwise bargains). As such, I didn't hesitate to buy a Camp 9 second hand (mint for $375 a year ago) and a Dutch carbine ($40

from a guy who was going to turn it in to melt it down) in the now-extinct 6.5 Dutch (which "Optimist" says I can make from .303 Brit. Thx dude).
I can't imagine that I did myself a disservice buying those two rifles, instead of another one in the calibers I already had. If the survival of my household relies on the difference between buying those two, versus another Mini 14 or 2 SKS's, then I'm doing something massively wrong elsewhere in my preps.
If I only has ONE of each of the other rifles, I could see a flaw in the plan. If I broke my only SKS beyond repair, for example, I would be sitting on cans of 7.62x39 that were useless. But I can't see lowering the bar on what I enjoy, just out of fear that I might break a handful of SKS's and all of the spare parts I have.
Quite frankly, I don't anticipate having to engage in firefights.
EDIT: Some of the less common calibers are just plain fun. I'm not Rambo. I use what I like. If this were the military, I had better get used to 5.56 out of a short barrel. But it's not. I would rather have what I like and like what I have than feel obligated to use what everyone else uses, and only what everyone else uses.