Are there any alternatives?

Yes, the Core i9-12900K is so close of an alternative that it’s almost identical — and it’s $200 cheaper. Otherwise, you could save some money with the Core i5-12600K if you’re primarily focused on gaming and don’t need the multi-core power of the i9.

　　

How long will it last?

Right now, the Core i9-12900K — and by extension, the Core i9-12900KS — is the best processor you can buy. It will last the next few years for intense tasks like video editing and transcoding, and for several more when it comes to gaming.

　　

Should you buy it?

No, buy the Core i9-12900K instead. The Core i9-12900KS is a product for bragging rights, and Intel is taking advantage of that with an obscene price hike. The differences for $200 are so minor that they’re irrelevant, and in some cases, it even seems that die-to-die variation can play a role in performance.