I wish I were more aware of what level of burnout there is in other large open source projects. Is Rust unique? Better? Worse? How do other projects manage this (if in fact they do)?
Projects like GCC and the Linux kernel do almost all their development in the open, via mailing lists, so maybe it would be possible to analyze that data to determine, say, the rate at which contributors drop out of the project. But I'm not aware of anyone having actually done an analysis like this.