Years ago, I bought one of those solar crank emergency radios. The instructions said that the battery will charge in sunlight, and if it isn't charged you can charge it by cranking it. So I sat it in an area that gets sunlight and forgot about it.
Years passed before I had a power outage, and when I did, the radio didn't work. Sunlight didn't power it. Cranking it didn't power it. It seems that, in the years that elapsed, the battery lost its ability to hold a charge.
When I first heard of 72-hour kits, I bought a bunch of bottled water and canned food. I put it all in the cupboard and forgot about it.
When I next moved, I dug out my supply of bottled water, and discovered that the water bottles were all kind of soft and collapsed. It turns out the plastic in the bottles wears out even if it's just sitting around doing nothing!
Googling around the idea, I also learned that canned food can go bad. People on the internet speaking positively of the longevity of canned food are like "Oh, it lasts forever! Like, maybe even as long as 5 years!"
Okay, but my life expectancy is far longer than that! Am I supposed to keep throwing out and replacing my emergency kit???
Googling around the idea, I discovered that the idea is that you use up the canned food and bottled water for your naturally-occurring everyday use before it goes bad, and replenish it. But the thing is, I don't really use canned food and bottled water in my regular life - I'd have to go out of my way to eat and drink it when I don't even want to!
Similarly, you're supposed to test your emergency radio regularly and replace it (or replace the battery if, unlike me, you've stumbled upon the convergence of a radio where you can get at the battery and a battery where you can find an actual replacement, not just something that claims on Amazon to be a replacement but is the wrong size)
Someone really should come up with an emergency kit with actual longevity, where you can set it and forget it without adding "constantly monitor your emergency kit" to your ever-growing to-do list!
One thing I have tried is storing water in glass bottles. I used screw-top wine bottles that I washed in the dishwasher in a sanitation cycle, and specifically chose bottles that had contained red wine in the hopes that it they didn't get perfectly clean, it would be visible.
I drank some of the water after a few months and it seemed fine, no ill effects or weird tastes, but obviously I have to wait multiple years to see if it lasts multiple years.
Another thing I realized during my last power outage is, canned food aside, I normally have 72 hours of food in my home anyway.
I usually have one or two perishable meals of leftovers in the fridge, which could be eaten cold right away before they go bad. I keep a couple of loaves of bread in the freezer that could be taken out and thaw, I usually have a variety of fruits and vegetables that are kept at room temperature in the supermarket (even though I keep them in my fridge for space and health reasons), I have a few bottles of meal replacement shake for if I get a reflux flare-up - basically, with no particular effort, I have 72 hours worth of food that's within the scope of what I'd eat anyway.
Last power outage when I realized my emergency radio had died, I looked around for if I had another radio around, and realized I still have my high-school walkman in a drawer. It takes AA batteries (which I keep on hand anyway, and could easily take out of a remote control during a power outage), and gets a better signal than my emergency radio or my bedside clock radio. So I'm not replacing my emergency radio, and instead just using my walkman for as long as it survives.
Thinking about what I already have around the house that would serve me well in an emergency gets far better results than making an artificial emergency kit, not keeping up on the additional chore of maintaining it, and then finding myself without an emergency kit in an emergency. Maybe advice surrounding 72-hour kits should focus on this?
But it would also be useful if there was a way to make universally set it and forget it 72-hour kits, so anyone, regardless of their needs, can just buy or assemble the kit and never have to think of it again.