Basically, we ask that you do so not as a last resort, per se, but sparingly. Rather than post the same thing here and elsewhere from the getgo, post one place, and if you have trouble getting help/get redirected, post here, but be sure to link to the other posting/keep both ends updated with any solution.
Part of being a friendly, welcoming environment is respecting the effort everyone puts into helping one another, which certainly includes making sure no one wastes time addressing a problem that's already been solved elsewhere.
EDIT: Oh, just saw @EconomiCurtis' post above:
I ~stand by my point re. immediate cross-posting â definitely when it comes to filing GitHub issues, at least, and give things some minimum lag time between sites. There's no way to keep track of things simultaneouslyâŠ