Do you mean as high as 3 seconds, or as low as 3 seconds? C++ compile times on a template heavy project I used recently were in the hours- you'd basically compile overnight and before you went to lunch.
a) #include <vector> -- Lots of dependencies, but I know it works and I don't want to reinvent the wheel
b) #include <my_vector.h> -- Ok, I'm going to reinvent the wheel, but at least my wheel might have slightly fewer dependencies.
c) //#include <vector> // I'll just do without the wheel entirely