Longer/shorter incoming enemy warnings for challenge modes

The enemy incoming indicators in experimental 0.27.1 feel good to me (compared to the game before, it feels almost like cheating :D) but I've also seen comments that longer forewarning would be nice.

So, maybe tie this into challenge modes? Longest on practice, longer on normal, same or slightly longer on Elite Enemy and/or Nemesis, same or slightly shorter on Mayhem? Only slightly, since the value of a particular length of forewarning is already lessened when enemies are stronger.