I tried to change some constants in random places(in 1 line each time) and on average it's ~10 seconds
Also compilation unit in rust is a crate. I guess if your app can be separated in different crates it can ease the pain.
Compile time. For my 9k lines project it takes 20 sec to compile in debug mode and 1 minute in release. Wich is insane because I have to do a lot of runs to test things(where cargo check can't help).