I'm using tags on a project that will need to work over a number of years. Will normal NFC tags still work or do I need active tags?
How long do NFC tags work for ?
You need to consider two aspects to this. The first is the physical tag itself and the second is the NFC chip.
The physical aspect is, for example, the adhesive on the sticker or the plastic surface. If the tag is in exposed conditions where it might be subject to rain or freezing temperatures, then it can fail if it's not the right material. Using a simple paper face label for example in outdoor mountain wayposts is not likely to bring you much success. Therefore, consideration of the environment in relation to the choice of tag is important.
Having said that, a plastic face sticker attached to a clean, dry surface can last a very long time even if in a relatively exposed position. A plastic face label indoors can last for many, many years.
Secondly, the chip itself. Most NFC tags such as the NTAG series have a memory specification of 10 years. In reality, it's likely to be much more than that but that's the spec. If you need longer than 10 years, then you need to go for something like the ICODE SLIX which has a memory lifespan of 50 years.
It is possible that the tag will not respond properly to a scan. It won't alter your data, for example change a URL or provide a different UID.
Seritag have been selling NFC tags for over 10 years. Some of the early NFC tags had a specification of only 5 years or so and all the tags we have from the early days still scan.
The actual lifespan of a tag is going to be connected to the environmental conditions the chip is exposed to and we would expect that in normal 'indoor' conditions for tags to go well beyond 10 years.
However, for longer term asset management, then it might be worth considering the longer lasting ICODE (or NTAG424 which use a different tech) chips which can last up to 50 years.
for what it's worth, I've got an nfc tag purchased from the old rapidnfc store that must be slmost ten years old and still works just perfect