Hackintosh is just great. I've had mine for about four years now, it's an Ivy Bridge series i7 at (I think) 4.3 GHz. I haven't had any need to upgrade the CPU or motherboard so far.
Last year I upgraded the 2x GTX 670 graphics cards I was using and put in a GTX 1080, in anticipation of Nvidia drivers becoming available. Of course that never happened and most likely never will, so now the Mac side of things is only running the integrated GPU (I sold the 670s). Still, it's very good in Windows and I could always get an additional 970 or something like that if I need more power for the Mac. I use it for writing, music and photography, so the iGPU is currently fine.
For major OS releases I wipe the hard drive and do a clean install then recover from Time Machine. Works perfectly. Other upgrades just use the standard App Store installer. The only thing I have to do afterwards is reinstall the audio driver, otherwise the headphone port doesn't work.
I've got an infrared receiver from an old Macbook Pro in there, plus a DVD writer, several extra USB ports and about seven extra hard drives / SSDs in the case. All things Apple does not cater for any more. If they ever brought out a new Mac Pro tower that allowed for that stuff then I would eventually go back to buying Apple hardware. Pigs might fly...
After being so very successful with my first hackintosh build, I succumbed to a fantastic bargain on an HP Elite 8300 for $200 a few months back (although, I still have yet to find a real use for it...). It featured an Ivy Bridge i7-3770 and UEFI. Installation of macOS Sierra was ridiculously easy and I was up and running within hours of receiving delivery of the computer. I have been extremely pleasantly surprised by how well it performs.
I haven't done a clean install in over a decade. When I transitioned from my MacPro5,1, I installed the Clover boot loader on top of my existing MacPro5,1 boot drive and then moved the drive to my hackintosh and continued to use it as is. Of course, I keep backups but haven't had to use them since I began using SSDs.
Yes, I also jury-rigged an Apple IR receiver to my system so that I could use an Apple Remote with it. I currently have three 3.5" drives, three 2.5" SSDs, and an M.2 AHCI SSD crammed in to my little case. All the 3.5" and 2.5" drives are in tool-less hot swap bays.
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I am also very happy with my experience at building and hackintoshing with basically the same results as you. I don't plan to update although as you say it would only require a MB and CPU replacement and the costs could be recouped by selling on ebay. My system is rock solid and I have even dialed back the OC from 4.8 to 4.5 just because I don't need it. The system idles around 23C and tops out around 65C and silent.
The only problem I have is Apple not supporting the Nvidia GTX 1070 I use to game with in my Windows 10 boot partition. I had to plug in a AMD RX 460 to use with my Mac partition.
I've been fortunate and have managed to keep my system inaudible
to my ears even with my overclock. To say that I'm extremely impressed with the Noctua heatsink and fans would be an understatement. They have performed well beyond what I could have ever hoped for or expected. I am still stunned at how the Noctua heatsink remains
cool to the touch even under full load. I never expected this since the heatsinks on my old MacPro5,1 would almost burn under full load, especially after upgrading to a pair of 130W X5680 CPUs. One thing that I did learn is that your choice of graphics card and the type of cooler it uses can have a noticeable impact on CPU temps.
As we all know, quite a few people are disappointed at the lack of Pascal drivers for macOS. Unfortunately, based on clues that I've seen, my guess is that there's a very good likelihood that we will never see Mac drivers for Pascal. As I've stated elsewhere, at this point, we can only hope that AMD's offerings improve and retail cards will work well with the drivers.
I feel like we are reverting back to the graphics card situation we were in back in the PowerMac days. Little to no options other than a few OEM ATI cards...