There's a part of me that always wants the IEMs that I own to have a resell value. With a custom, once you're past the 30-days or so that you have to return them, they (in my mind) become somewhat "worthless" as they usually can't be sold (unless someone buys it from you with the intention of reshelling it somehow).
I also don't really know if customs are the end all be all anyway. It seems that universal IEMs are making big strides in comfort and sound.
One neat versatile thing about the universal SA6 vs. customs is that the sound can be tuned to the listener's preference. That's how they were designed and it does work to some extent.
I've often also read about people who get LiveWires/FreQ's and actually end up preferring the sound signature of one of the universal IEMs that they also own (a la Shure SE530 or UE Triple.fi 10 Pro). Head-Fier EyeAmEye I believe even prefers the Sleek Audio SA6 over the Ultimate Ears UE-11 Pro. FeedMeTrance preferred the sound of his UE Triple.fi 10 Pro over his LiveWires before (not so sure anymore). antonyfirst and many others feel that the STAX SR-003 is the best sounding "in-ear" 'phone. HeadphoneAddict says that the Klipsch Image X10 is nearly as good as his FreQShows, but also I believe he really enjoyed the Westone 3 when he demoed them. So on and so on...
The Westone 3, when it eventually (and finally) comes out, seems to be able to compete handily with custom IEMs while also retaining good resell value.
One thing that I've also read about that is a bit more rare is some people's sensitivity to hard acrylic inside their ear. Or, I believe Sovkiller has had trouble getting customs to work for his ears for a reason pertaining to his ears specifically.
Also, it seems to me that there are plenty of people who do not want to deal with re-fits/re-dips as it seems it is often needed to achieve a good seal reliably.
One thing that is nice about universals is that you can share the sound with others so they can find out what they're missing out on. Try doing that with custom IEMs.
I don't think there is one set straight-forward path that everyone should take (i.e. going straight to customs) on the way to audio nirvana. Many of us are plenty happy with our universal earphones.
When you get your LiveWires and if you're 100% happy with your purchase and feel that you're done with the journey, then that's great for you, but realize that not everyone will think/hear the same way as you do.