I do have a sense of unease about most smaller hosting services and self-hosting solutions, in that I don't trust them to stay up in the long term, once no one is left to care about projects on them, or at least not about the old versions. (This isn't so big an issue for something as big as FFmpeg, but I'm talking about the general case.) Just try to download some old version of a minor library from the late 90s or early 2000s: unless it's been continuously using the same source control repo, the odds are better than not that the files disappeared during the intervening decades.
In contrast, whatever its faults, I fully expect public repos on GitHub to last for the next 10 years, likely the next 20, barring active removal by the author. (The biggest medium-term risk is a "GitHub is evil, take down all your repos" campaign a la Reddit.) Of course, it's not foolproof, the only way to get that would be to replicate the project in dozens of places, but I find it much better than the old status quo of files slipping away once forgotten.
