While things have changed for ring slings in the regulatory sphere, all my custom-sewn slings have passed the sling standard, and the clearance section, having been sewn before the standard took effect, is exempt.
Current turnaround time: 2-3 business days (due to water sling BOGO 50% off sale)
I don't sell anything I wouldn't personally wear or recommend, so in that respect, I don't think you can go wrong. I research the properties of the fabrics I choose carefully, and am confident in their safety and longevity. (Of course, slings are just fabric, and there's no magic in them -- they will eventually wear out, and the more they're used and washed, the faster they'll wear out. They are also not colorfast against sun damage -- that takes chemical treatments that I would not want next to my baby's skin -- or bleach, so if you're out in the sun, expect some fading.)