Headphones

If I purchase one of these, will I ever be truly satisfied with just the one pair?

No, you'll get the itch to try other shit for the novelty at some point, especially as you haven't learned your own preferences.

Of those three alone I'd never touch the Hifimans, none of their planars have a correct sounding tonality while their build quality and QC are legendarily terrible, blind buying a $1000+ Hifiman as your first headphone would be downright stupid. Clear MG is tuned a bit dark and while Focal QC isn't Hifiman-level bad it's also not great, so I don't think that spending $1500 on those blind as a first headphone is a good idea either.

Find an audio store near enough to you to be reasonably accessible and go demo some headphones, spend some time with each one to get a feel for them, and demo cheaper models in the $200-500 or so price range as beyond that you're paying a lot of money for little or no actual improvement. Most kilobuck headphones have something wrong with them that requires fixing via EQ because at that price point they're selling to 'audiophiles' who are constantly buying new shit for the unique flavours, not people seeking out a quality neutral sound.

tl;dr just buy a 6XX or 560S if you can't go demo and don't buy Hifiman unless you're comfortable with treating them as disposable