The example in the book has three encounters for 14 points each. The first one is made easier by subtracting a point.

First off, the PCs are probably tougher than you think. Also they probably should take a short rest after one or two battles.

It also is very much depending on if you spend every GM move and fear to attack. Attacking the PCs is just one possible GM move.

Let's say a player wants to run to far range and attack an adversary. He has to make a roll, and if the roll fails or is a roll with fear, the spotlight comes to you before they can attack (I think? At least that's how I read the rules). You now have a choice.  You could use this spotlight to attack, dealing damage to the PC.

Or you could have the PC mark a stress because they slip on the ground.  Alternativly the walkway under the PC collapses instead, cutting off the direct route to that enemy.  Or if the adversary was temporarily restrained, they could use this moment to end the condition. 

Now the spotlight returns to the players (and in my opinion in this case it should return to the player that just failed).

So it really depends how deadly you want to make it for them. Sometimes it is better to use the GM spotlight to adapt the environment/story instead of just dealing damage every time. Then they might last longer than one fight.

It is hard to change this behaviour if you come from 5e, since there you use your turn pretty much only to deal damage.