I have a USB stick with a gold plated metal casing plugged into my laptop more or less permanently and today I noticed that it gets quite hot. Is there any danger that it could overheat and result in the destruction of the data on the stick?

Have no idea of any real such danger but it does appear to be a very old model so would replace myself. The newer models run much cooler.

You shouldn't have the only copy of your data on a flash-drive anyway.

Keep a backup in the cloud or on magnetic media.

Use a reliable brand, I have used many brands over the years and I have found Kingston the best.

I have never had a Kingston fail nad I have several nearing 8 yeras old.

I doubt it. The heat is probably from a fan vent nearby

Am not sure what you doubt but can confirm older thumb drives can get very hot during use.

Thank you all for your replies.

I am not using the USB stick for the backup. It has a copies of a couple of files that are on my desktop PC and get backed up there. I don't want to save them on my laptop's hard drive or store them in the cloud.

I used to have the stick in a USB slot on the left side of the laptop, where the battery seems to be as that side gets warm. Two days ago I switched it to the right side and I see not difference in temperature. It gets warm even though I access it rarely and even when it is not open in Windows Explorer.

The stick is indeed quite a few years old and with all the information I received here it now looks obvious to me that the heating up is due to its age, ie its being an old model. For a moment I was thinking that the metal casing was serving as some sort of heat sink to dissipate the heat created when it was processing data, but as it remains hot even when it is not in use this cannot be the case. It doesn't get burning hot, but when I hold it between thumb and index finger I can feel the heat. I rather like it because of its small size (and its gold plating) but if ever it should fail I will suffer no harm and copy the files from my desktop to another small USB stick that I have lying around, probably another old model.

This got me to wonder: how can I check whether a USB stick is an old model, whether it is USB 2 or USB 3?

Unless you bought it in the last year and a bit, it will be USB 2.0. Unless its very old (10 years) and about 32mg in size.