How long does a decent USB stick last?

Until you store indecent stuff on it.

I've had some for 10 years+.

4GB

The first usb stick I bought more than 15 years ago, still works.

I’ve quite literally never had one fail even under heavy abuse.

I tried several random cheap sticks recently and they all died within a year.

A funny story: In my second grade at school, I got gifted a 4gb stick for winning something related to IT, it was around 2009. It worked all this time as a distro stick, until my PC couldn't see it anymore. I thought it died, but I tried it a year after and it magically works again now

As someone who works in IT since 2005 I haven't seen many die. Then again we barely use them so maybe in my life I've handled about 10-15 and seen 2 die. One in spectacular fashion when our department gave us all one since they thought it was a tool that was needed. Every single one of them ended up dying within the year. Just goes to show quality of the product can matter significantly sometimes. Outside that, they are pretty reliable, but I also would trust them the least out of the other options available for storage.

In my experience, they last until you look at the capacity a few years and several changes of use down the line and end up giving to someone for some weird reason with a single MS document filling it up.

Can be years, but it's as much luck and storage conditions as anything else. Luck being that batch of components not having one tiny error, or the box not being dropped by a guy loading the truck.

Get 2 backups from 2 different high end companies. Store them somewhere cool and dark with little to no moisture, in a static bag. So a ziploc with a silica gel packet in a safe in a basement. Or even in a fake soda can in the back of your fridge.

Obviously there will be backups, but I also don't want to lose anything on it as much as possible.

Don't rely on a USB stick for that, no matter the brand, at least based on my personal experience.

I still use one I bought in 2007.

It's pretty random.

Carried a LaCie IAmAKey on my keychain for 10 years before it died. Probably used it a dozen times.

I have some 1gb sticks that are about to turn 20 years old.

I have seen only a single usb stick die

It was a 2GB one bought a very long time ago

The only one I ever had break was one I accidentally smacked pretty hard perpendicular to the USB port it was in, and I'm still not 100% sure if it was the port or the stick that broke. It sure scrambled the directory listing in the file manager though. Lots of funny characters.

Pretty sure the port took damage because it didn't work well with other things plugged in afterwards, and I've never used the stick again in case it's turned into a port killer. That probably just me being paranoid though.

I think the real danger might be write cycles. Super cheap ones might run to only a few tens of thousands of writes per cell and might even do no wear-levelling, bringing that down further. Nonetheless, as I understand it, they usually lose write-ability before read-ability, so in theory you'd be able to get data off one you couldn't write to any more. (In practice might be a different matter.)

Actual physical lifespan ought to be more than that if it's in regular use. I have a 256MB one that was just shy of state of the art when I got it (must be coming up on 20 years old) and it still works fine. I don't use it often though, so that might be in more danger of old-age rather than data integrity problems.

Honestly, this vastly depends on the type of drive, and who made it. I have had cheap drives fail after 6-7 months of usage before but, that was because I was using it for external storage for an RPI so it was doing a lot of writes.

Using it for a write few read many style system(like bootable OS images via ventoy), I had had flash drives that have lasted 10+ years now. but I wouldn't recommend using them for anything that was super write heavy.

I've always managed to lose them before they die. Current senior partner of the group is a 4gb HP drive circa ~2013. My loyal document carrier.

USB sticks are a consumable, they should not be treated as anything but temporary storage.

I would look into an external SSD instead.

This is my professional opinion as an IT technician.