You're right, "stable" compared to other similar artificial elements is still very short lived, however, the stability of heavier elements is ultimately undetermined. They could be a lot more stable. I remember my p. Chem professor talking about this some, many years ago actually... It's an unknown that warrants scientific exploration.
But back to lv 426... I still think it makes more sense that any mining, at lv 426 or elsewhere, would be for some specific rare isotope or this exotic material mentioned in out of the shadows called trimonite.
And lambert misspoke. Haha
Oooor.... Lv-426 is really made of dark matter! Jk :-)