Ecclesiastes 5:10-11 with a few words replaced in brackets:
The one who loves [guns] is never satisfied with [guns], and whoever loves [ammo] is never satisfied with [his stockpile]. This too is futile. When good things increase, the ones who consume them multiply; what, then, is the profit to the owner, except to gaze at them with his eyes?
Panic and fear are huge motivators for gun and ammo sales.
While it is wise to prepare for what may happen in 2020, fear...
has some folks buying ammo they will never be able to shoot in their lifetime
Any number posted is just that... a number. It doesn't account for how much a person enjoys their hobby.
It is wise to do the math. How many times do you go to the range? How many cartridges do you shoot on average? For instance, one person buys a case of ammo that lasts them 10 years, while another person buys that same case, but it may not last 10 weeks. That is why posted numbers don't matter, it does not take usage into account.
While it sounds good to say X number of rounds for every caliber. Do you shoot all your calibers equally? Most people do not. IMHO, it would be more beneficial to weight the calibers by usage and have more of what you use more often.
I'm not saying that it isn't wise to purchase JHP's or to not take advantage of deals or rebates. However, it is my personal opinion that
hoarding JHP ammo is a silly thing. Why? Because the usage is even less than target ammo. Some people hold on to their GoldHSTDutySabers as if they were are a priceless commodity. I'm not saying some flavors of your favorite defense carry load aren't scarce. I'm just saying to be smart about it. Carry ammo needs to be switched out because being on your person is not a cool or dry place. You can decide the interval on your own. If a person shoots up your what is in their carry mags, checks zero on their CCW, even chrono's their defensive load, and then reloads the mags - for most people, they aren't even shooting 50 rounds of JHP's per year. The point is to count the cost and your timeframe. Also, since JHP's are somewhat of a technology product, be prepared that your precious GoldHSTDutySabers will not be the new hotness when version 2.0 comes out or some paid advertisement YT wonk promotes a new and improved product offering.
The last thought is to prepare for what people who don't know any better will want to hoard. 22LR, 5.56/223, and 9mm are givens. Remember, there was a time when 9mm was almost unobtainable, but 40S&W, 45acp, 38/357 were just sitting on the shelves. There was a time when Cabelas wanted $20 for a 20 round box of Remington 55gr FMJBT 223. There was also a time when a WM hoarder was trying to get rid of his $11,000.00 22LR stash because he realized that the drought was over. WM (if you even go there anymore) and your big box outdoor store will typically still have your deer hunting caliber on the shelf. At one time during the drought, I was shooting a lot of 308Win simply because it was always available.
All that to say, be wise and prepare for the future, but there is no reason to panic. Even presidencies are limited, just as our constitution reads.