In my day to day there's about 30 seconds for a cold compile (which is rare, only when I clear byte caches) and maybe 5 seconds usually, less if I've just changed one line or something small like that.

That said we're not using GWT for CSS, so that reduces iteration time where it's most noticable.

With TeaVM, I can do all my iterative development on the JVM (instant compile time). Compiling to the browser is usually just a one time thing for deployment. Although, TeaVM also have a "dev-server" mode that does iterative compiles, which is apparently much faster for iterative development.