Dick Long :
I just want a computer that would last a very long time without having the need to upgrade for a while, not forever
Yep. And that's not going to happen. If you upgraded the CPU to a Xeon (The one you have right now is NO better than an i5-3570k for gaming), this computer might last four, five, perhaps six years, if you stay with that monitor.
But new CPUs are coming out, new graphics cards are just around the corner. While these ones won't bring impressive upgrades, two generations from now, tech companies are going to be pushing high-density screens like crazy... and you won't be able to upgrade to one, and you'll want to, desperately.