FWIW, I have a 1TB steam deck with an extra 1TB SD card added—my storage is close to full.

Gotta remember some games these days can get ridiculously huge (100-200gb)

Switch if you ever plan on downloading more than like 4 games

I would use the second one as a backup.

You could use one of these USB SDcard reader and script something that backups the content of the running/live SDcard to the second one on the USB stick. With dd or something you could have an always ready backup SDcard of the RasPi system.

That or using an old Android phone as a media center and putting the second SDcard in that.

Or using an old Android phone as a surveillance camera but that would be a bit overkill to have 256Gb.

Also if you have an early model of the Switch you could hack it to run pi... homebrews and in that case having a super large SDcard could be good.

There's a Raspberry pi project you've been wanting to start. Sounds like now is the time.

Retro gaming is fun. If you don't mind pirating games, you can put all of the N64 games, SNES, Gameboy, lots of MS-DOS classics, C64, Playstation 1/2 games, Arcade games etc on it and play some Frogger or Banjo-Kazooie. That'll fill 256GB. Emulators are available on many platforms. Raspberry Pi, Android, PC, ...

You can also stick it into the SD-Card slot of your laptop and use it as additional storage.

If your devices are a bit older: There are adapters to use micro-SD cards in devices that only accept full-size cards. They come for free with some micro-SD cards or should cost a few cents.

archive.org has some old games. Some of them are legal to download or abandonware and somewhat a grey area. Illegal sources for 256GB torrents of old games would be something like www.arcadepunks.com or maybe rompacks.com but I wouldn't recommend pirating games from your own internet connection especially not with bittorrent.

Pi… with the second to be used when the first one dies? Every now and again I make an image backup of the sd card for my klipper install on my printer.

It should be in a shoe box labeled “flash cards”

Steam Deck is great and I'd recommend getting the base model then upgrading the drive to something bigger on your own in addition to using the SD card.

I bought the steam deck with the largest storage available, and still ended up picking up a 1Tb SD card. I wouldn’t end up tossing that idea unless you have a modest library without a lot of the big footprint games.

I’ve reached that point where I’ll spend some extra money to avoid the inconvenience of having to redownload a game if it’s at all unavoidable, and the internal storage gets filled up a lot faster than you’d think. You know your own library and habits, but you might be happy to have one on hand.

If it's a higher speed than the 64GB one in your Switch, it could make sense to replace it with the new 256GB one for slightly faster game loading times.

If you had a rooted Android I would have suggested using the SD card for primary photo storage, and app backups/"timeshift-like" restore. I use mine for both, as well as offline maps, app data, and some LLaMA models before the AI LLM novelty wore off

Well, I have one in my Wii, one in each of 3 Wii Us, one in my vita, one in each of 3 3DSs. We're you looking to hack any of those consoles?

Outside of games, you could use it in your desktop or laptop as a drive for different things. On my Mac, I use a 512GB for torrents instead of having it write to the SSD. I also have one that the Photos.app saves the Local iCloud Photo Library to.

Likewise, if any of your media apps let you set a default location, you can take advantage of it and have the apps and programs save content there, I do this for DVDs and Blu-Rays I get to have a digital copy.