I've used Macs since they came out. I used to routinely zap PRAM about once a year as part of regular maintenance or when boot problems arose. Over the years, maybe 5-10 years ago, zapping the PRAM didn't seem to help so much, so I drifted away from using it and didn't miss it. I love Mac Minis. I own two and work on about 20. I recently tried to upgrade one to High Sierra but it wouldn't boot after. I tried all the tricks I've learned about recovering from failed High Sierra upgrades, but I had to erase the drive a couple of times to finally upgrade that sucker. One of my own Mac Minis still has Sierra. I'll eventually upgrade it to High Sierra after one or two more macOS minor releases, i.e., .5 or .6. This Mac Mini sometimes won't boot. I once improved its boot time by running Disk Warrior but I leave this Mac Mini on and only restart it to install macOS security updates. After installing the last security update for Sierra, the Mini wouldn't boot. Not in Safe Mode. Not in recovery or single-user mode. Its Zeno-paradox boot-progress bar slowly millimetered to the right but never reached the end, even after running overnight. I planned to replace the hard drive but on the way to Damacsus realized I should listen to an old friend who's still a full-bore triple Zap-the-PRAM zealot. He claimed it helped his Mac boot faster after some recent slowness but I was skeptical. But I tried it again after all those years of zapping the heck out pram everywhere I went. Back in the day, and it might still work this way, repeatedly zapping the PRAM (holding command-option pr and not letting go until the Mac quickly partially reboots and chimes) used to reset "deeper" and "deeper" variables ("parameters," a hem) stored in flash memory (NVRAM) with each consecutive boot, or so we thought. I don't know if it still works that way, but what the heck. The joke fear years ago was that if you kept consecutive zapping the PRAM you'd go too far and zombie your Mac, but that was silly, ha ha, but I never tested it. About a week ago, my Zeno-booting Mac Mini got its PRAM zapped 3 times in a row -- chime, chime, chime (again, not letting go of command-option pr as the Mac cycles through partial quick reboots 3 times as represented by 3 POST [power on self test] chimes, after which let go). It worked! My Mac Mini booted quickly and continues to boot like a normal healthy Mac (I work on hundreds of Mac models so I have good reference points). Just for fun I rebooted it a few more times during the day. Eureka! Let's boot again and celebrate. I've repented and now even volunteer to zap friends' PRAM. If you see me on the corner with a megaphone, don't offer donations, I just want everyone with slow-booting Macs, especially Mac Minis, to zap the PRAM 3 times in a row. If it doesn't work, you just don't have enough faith or it's some other problem.