A Windows system should last at least a decade IMO so I'm with you on that. I have at least half a dozen PCs like that at home that still run great. This is the advantage of building your own: selecting a good system board, CPU, RAM, and storage. Graphics cards certainly are more of a user preference but one need not be a hard core gamer to appreciate the benefits of a good GPU. They are also very convenient for rendering, streaming, and assisting the processor (depending on how it is being used). I have a modest NVIDIA 1070 in my work station and although I could probably benefit from a faster GPU I find it suits my needs.
Cheaper is mostly the domain of pre-built systems and rarely can one build a PC these days that can match advertised specs in a pre-built system, like Dell, or HP, or Acer for less cost
BUT a close look under the hood can confirm that the hardware they use is hardly the quality of those well built systems an enthusiast is able to put together. Plus building their own PC helps the end user to get better acquainted with their computer as they get to know it inside and out. This is also a great way to dodge the bloatware that comes with pre-built systems and likely one more reason why it is still prudent to build your own desk top PC.
Newer is not always better either, I find. Again, it's a matter of user preference and some of those older features still have value. Like the old saying goes, they don't make 'em like they used to.
