You can usually get a noticeable speedup using unity builds, even when using something like Incredibuild. That suggests that more source files is not the answer

You can usually get a noticeable speedup using unity builds, even when using something like Incredibuild. That suggests that more source files is not the answer. (I am not going to speculate as to why things are this way; it simply appears to be the case.) I'm not sure it makes a great deal of sense to separate compilation time from link time anyway (and you should also consider device reboot or program startup time as well). It all adds up to the same thing: shameful turnaround times. This has been a problem on every C++ project I've worked on over the past 15 years, and it only seems to be getting worse. And scaled up by increasing team size, that makes it even more of a serious problem. I hope your parting shot was intended to be that we shouldn't have to worry about this today, i.e., that we should be able to expect more from our tools, and that the current tools are shit. Because we absolutely should worry about it! This is people's time we're talking about. That isn't any less valuable than it used to be.