My son (in high school) took into use a HP-15c that my wife bought in 1987. Alas, it broke after travelling back and forth between home and school for a few months. A true loss, but it wasn't as strong as I thought it would be.
In 1985, I was preparing for the matriculation exam (at end of high school). I was worried that my Sharp EL-506 battery would run out in the middle of this important exam, because it was already 3 years old. However, I did not change it. It lasted the matriculation exam. It lasted also my MSc studies and army, 9 years altogether. And beginning of my working career. And it actually still works, though nowadays I don't need it so it's just at the bottom of the drawer. But it is OK, 31 years after buying it, with original batteries and some significant use during high school and uni. I just don't understand.
My HP-48sx is 21 years old and I still use it roughly daily at home.
I have an emulator on my phone but the tactile response of the keys is awful and the display and keyboard are tiny compared to the "real" thing.
Its just too easy to use. Latency of the calc on my phone is very high compared to a fraction of a second. If my desktop is up and running and logged in and a webbrowser is running (lots of ifs) then google and wolfram alpha are starting to eat into the 48's territory. But it still gets plenty of use. Batteries last about a year.
I also have a 32Sii at the workbench vaguely 90s vintage.
TI has a pretty good gig going since they're selling a "calculator" and not a "computer". "Calulators" don't follow the same market dynamics as "computers", so as long as everyone in that market plays along and competes on features (or no one adds features) they should be able to maintain their margins ad infinitum
My HP-42S calculator is 23 years old and I keep it at home than bring it anywhere as it can be snatched easily and sell on eBay for 3x the original price!
In 1985, I was preparing for the matriculation exam (at end of high school). I was worried that my Sharp EL-506 battery would run out in the middle of this important exam, because it was already 3 years old. However, I did not change it. It lasted the matriculation exam. It lasted also my MSc studies and army, 9 years altogether. And beginning of my working career. And it actually still works, though nowadays I don't need it so it's just at the bottom of the drawer. But it is OK, 31 years after buying it, with original batteries and some significant use during high school and uni. I just don't understand.