Are there any alternatives?

Yes, several:

　　HP Omen 45L: Cheaper than the Predator Orion 7000 and equipped with Intel 12th-gen processors, but it doesn’t support DDR5.MSI Aegis RS 12: Much cheaper than the Predator Orion 7000, but the case isn’t great, and the machine is prone to noise and heat issues.

How long will it last?

The Predator Orion 7000 is powerful enough to last you several years, so you won’t have to worry about upgrading for quite some time. In the future, you can upgrade the components because the Predator Orion 7000 uses all standard-sized parts.

　　

Should you buy it?

Yes, but only if you can’t be bothered to configure a PC with a system integrator. You’ll get a much better desktop with Maingear, Falcon Northwest, or Origin, and you might even save some money depending on your configuration.