Sorry, that was my second question ever I think. I hadn't got any experience back then.
What I tried to ask was... Ash only substituted his pokemon when they defeated another one, in Unova, Kalos, and Alola leagues. For example, Pikachu and Dewott are battling; Ash wants to use another pokemon, so he waits to beat Dewott, and then he will use another pokemon.
He wouldn't do what he did in the Orange Islands and all those places. For example, Ash's Lapras and a Dragonite are battling; Lapras has taken a lot of damage. Ash will substitute straight away, not defeat Dragonite with his Lapras first.
Know what I mean?