The RPG I'm working on is going to use a battle system similar to Earthbound, Escheron, Final Fantasy and Illusiat 13, where you fight a group of enemies in a turn-based battle, walk around for an amount of time and then battle more enemies.

Please suggest what would be a good amount of time between fighting enemies.  If there are no suggestions, I will do somewhere around 30 seconds.

That's not what Earthbound does. it does it like CT, Enemies are already on the map, and when you touch them you fight.

Okay, so that's true, but unless you run back and forth like a maniac the amount of time between enemies is somewhat consistent  Besides, in "Earthbound Zero," it's a timing system where you don't see enemies

EDIT: Distance might be good, but then if you could suggest how many "seconds" of walking

Judging by the speed at which your screenshot ran, between 20 and 40 steps. 10-50 was used in old Illusiat games. Illusiat 13 used the same I think, but I'm not sure anymore.