Despite games only having a maximum of 4rounds. thinking a few steps ahead is very crucial in the game and unless your opponent is aware of your attack (10% of the time) he will lose the fight as he tries to beat you with fury in desperation.
so when should you think ahead? well the best time to use it is when you have at least one blocker in your hand.
another place which it is quite effective is in survivor. why? because players are scared to use pillz as they are short of them in survivor. its not as effective in elo but alot of noobs and unexpirenced players will fall victim to this every time.
your hand: cooper, Chloe (R) (R), Uranus (U) (U), grammxxt
you have 1 nuke and three blockers. so you should think right i have alot of damage with cooper so if i can deal alot of damage to my oppenent then i can block for the rest of the game. so going all out or at least 8 pillz (just in case) and blocking the rest of the game will asure me of an easy victory.
In conclusion thinking a few steps ahead is an important skill to learn and will serve you well in many games to come.
so when should you think ahead?
Every game? And in your given scenario, you won't attack with Copper round 1 and go all-in right away. Graksmxxt and Uranus are also great damagedealers and noone want's to pill against them because they will invest x pillz for 1 damage most of the time.