Nintendo wants to:
Know your location.

Allow / Block? _

Not always. Certain 3DS games require either lot of horse power and some don't play well without touch screen or a second screen. I also recommend to get another 3DS and hack it, and dump all your games as Roms to play on the hacked machine without emulation. So that way you preserved your own save files and games at least for yourself, in case they say "bye bye" to you. Otherwise, yes, emulation is your friend. :-) (Me a big emulation fan, BTW.)

My hacked 3DS is all I need.

Bookmarked for later, going to load up all my old games tomorrow.

This neighbour comment might be for you.

Yeah, I tried booting an emulator handheld I've been gifted a year ago and pretty much hadn't played since then, and the battery didn't hold more than a minute of charge. Moreover, while googling for replacement batteries, I came upon an article saying this and some other devices have screws positioned such that the heads pierce the battery if it ever starts swelling.

Yeah dude, 10 years ago was the 90's

Short answer: It depends. Doing full flash reads of your USB sticks and SD cards (dd if=/dev/XXX of=/dev/null bs=4k status=progress) may help for a lot of them. But not all. The only solution I can actually recommend (for any storage media) is backup them up and regularly testing/moving the backups.

If the read of the disk is particularly slow then that indicates the flash cells are degraded. If a second read of the disk is much faster then that indicates some action may have been taken by the flash controller IC to fix this.

Long answer:

NAND flash cells slowly leak charge, making their state indistinguishable. A flash controller IC (usually separate to the NAND flash IC or ICs) has the job of noticing and fixing this (by rewriting the data to another or the same cell) before it gets too bad. That doesn't necessarily mean it does it particularly well.

Some (few?) flash controllers periodically scan for weak cells and rewrite to fix them. Some (most?) flash controllers notice weak cells only when you read them. Some (many?) flash controllers are shit and don't do any of this.

Flash controllers also have a bunch of other features and jobs, like maintaining a spare pool of cells (over-provisioning) to swap out for bad ones and even forcing the USB stick into read-only mode if they think things have gone particularly bad. Again this varies a lot depending on implem, some do it, some don't, and for different reasons (out of over-provis cells, corrupt mapping metadata, arbitrary thresholds, etc).

USB/Flash memory is not an archival storage medium. It is far to volatile, so as long as you are not using USB sticks as an long term archive for precious, irreplaceable documents/data, it shouldnt be a big deal to you.

Flash memory will self-erase if left idle/unplugged for a long enough time.

Mechanical hard drives can be archival, but you cant just load them up with data and shove them in a closet.. They need to be hooked back up and spun up every month or so, to keep lube moved around and keep platters and arms freely movable.

I think it's that the actual game itself gets corrupted. So it's not even that you can't save, it's that you can't play the game.

Like @ClipperDefiance@piefed.social pointed out in this thread tho, there may be ways to save a corrupted game.

Your LttP cart, assuming you already changed the battery, could have a bad SRAM chip. You can FRAM mod the cartridge to both save it and remove the requirement for a battery at the same time.

Also worth checking all the traces from the cart connector to the SRAM chip.