This reminds me of the discussion that I had a few weeks back with the wife, she was looking at saddles, she has three already, and was looking to buy the forth. Now she only has two horses, and I couldn't resist saying, hey honey are you looking to get some more horses? This puzzled her and she replied in the negative, and asked me why I was asking? So I explained that she only needed one saddle per horse no matter how nice they are, the other's will just end up collecting dust in the tack shed. She didn't get my drift, until I said that I have 26 mags for my 2 AR's, so I get to go buy another AR or 11. Guess I should have left her to it, the cold shoulder treatment got boring on the third day.
It also depends on if the user just plans to be a survivor or if the survivor plans on banding together to protect the group in the short term and help bring back the Republic back in the long term. It would also depend on your METT-T (Mission, Enemy, Terrain, Troops and equipment, and Time available) and OCOKA (Observation, Cover and Concealment, Obstacles, Key Terrain, Avenues of Approach (battlefield terrain)) Everyone will make there own choice. Just for info I was Infantry for 12 years. Where I live if TSHTF or TEOTWAWKI this are will burn itself to the ground, and I plan for that. I also plan for SHTF in various degrees (A page taken from Ferfal). I do not know what the future will bring although in my estimation it will not be good. Any combat vet will tell you war is the last thing they want to see but if it comes so be it. I have been shot and if not for the plate I would not be typing this now. I also plan to honor my oath of enlistment if it every comes to it. I'm in moderate health and exercise and train just because it's what I like to do. To each his own, do as you see best. Nomad 2nd, are you the same one on SurvivalBoard?
The question is not how much you need the question is can you afford to have too little. One of my hunting shotguns is magazine fed so there is a long mag sticking out the bottom. Now the guys that I hunt with only carry five or less shells with them when they are hunting. I carry four five round mags. They laugh and ask me if the deer are going to fight back. One day I was hunting and shot at a deer, missed, shell did not eject, drop the mag, cleared it, pulled out a new mag, snapped in the mag, chambered a fresh round, hit the deer, it did not drop, shell did not eject, drop the mag, cleared it, pulled out a new mag, snapped the mag in, chambered a fresh round, deer ran past me, shoved shotgun muzzle in deer’s butt pulled trigger, Hit the deer, it did not drop, shell did not eject, drop the mag, cleared it, pulled out a new mag, snapped in mag, chambered a fresh round and after deer ran {crawled} fifty yards the deer gave up. I used all four mags that day. Shot gun is now fixed. The point is what if you drop a mag and lose it, dent one or bend the feed lips on one? If you start out with five mags you could be down to two before you know it, then what?