I have just built the sig Skylake, with a few loose ends to tie up. It is equipped with dual-boot OS sharing 1TB NVMe, a 2TB 2.5" Seagate similarly split down the middle, and a 1TB shared 2.5" drive for video captures and other common files. Much of my important "stuff" is on a server. I expect that the first two drives may fill up half-way eventually, and the third one depends on a future inclination of mine.
I can only say that today is much better than some years ago, when I would wring my hands and fret over which 500GB HDD to buy, or painfully selecting an SSD with decent capacity that I could afford at that moment.