A problem with the original poster's thinking is that one or more major concerns are being overlooked. First concern is that will the store bought ammo always be available at any price? That is a real uncertainty. Second concern is that if it is available in the future, at what price will it be? I ain't got a crystal ball, but I am certainly willing to bet good money that IF ammo is available in the future, whether it be a year from now or 10-20 years from now, it WILL be more expensive. That is IF it can be had. Lay in the loading equipment and components now and don't worry about it in the future. Case in point: I started reloading several years ago and can reload for just about everything I have. This includes 9mm. When I started this, I could buy in bulk "range ammo" 9mm for about what I could load it for, not counting my time. Many thought I was foolish to do so. I learned by doing so and mastered the art and laid in a good supply of components at what now would be considered very cheap prices. Back then the prices were common everyday market prices for not so long ago. Then, suddenly, the ammo supply disappeared and soon followed by component shortages and even reloading equipment shortages. Nobody had extra ammo to shoot anymore at the public range I frequent. At least not near the amount of shooters there and those that did still go did not shoot near as much. I still have been shooting as much as I always did. So many others for a while now have been crying about no ammo to buy and too expensive when they do find it. I'm still shooting as much as I want.
Now, having said that, if one is pretty sure they will never shoot more than say a 20 round box - or less - per year of hunting rifle ammo and they figure they may hunt for maybe another 15 years, then go buy 10 or so boxes of good quality ammo and forget about it. I know a lot of hunters who shoot 5 or less rifle cartridges a year. Speaking for myself, I like to put two deer per year in the freezer. Last year I used 4 rounds to do that. That included two rounds to check my zero before going hunting. At that rate, two boxes of cartridges would last me the remainder of my expected hunting life. Pistol shooting at the range is a whole different proposition.