Are there any alternatives?

There isn’t anything like the Core i9-12900K on desktop right now. The closest competitor is the AMD Ryzen 9 5950X, though it’s not nearly as fast as the Core i9-12900K.

　　

How long will it last?

The Core i9-12900K will last for the next several years at least. If you’re buying a processor as high-end as the Core i9-12900K, you’ll likely upgrade before performance becomes a major issue.

　　

Should you buy it?

Yes. Right now, there isn’t anything that performs as well as the Core i9-12900K. That said, it consumes a lot of power, so make sure to buy a beefy power supply and cooler alongside it.