Not necessarily. If you lose with one combination, then you can try with the 4th you have.
Gyms are a joke now because we can just squad up with 6 when they only have like 2. That's why I respect Giovanni and Blue because they had some high numbers with them.
I can easily stall out leaders until they run out of PP with their threatening moves. I mean, if Ash can do it in the anime...I think we can, lol.