Are there any alternatives?

Yes. You can find a host of machines that match the Maingear Vybe, and you can build an almost identical copy yourself:

　　Origin Neuron — More expensive, but much higher case quality and more control over components.HP Omen 45L — Cheaper and with a better case design, though much larger and with a few minor build issues.MSI Aegis RS 12 — Slightly cheaper and better case airflow, but poor build quality.

How long will it last?

Given the components inside, you can expect the Maingear Vybe to hold up for several years without upgrades. That’s one of the reasons to go with a company like Maingear, though. You can continue upgrading the Vybe for as long as you want.

　　

Should you buy it?

Maybe, depending on your budget. If you’re on a strict budget and want the attention to detail boutique PCs bring, the Maingear Vybe is a great option. Spending a little more can net you a high-quality boutique option, however, and you can give up some build quality while saving money with a mainstream option.