Do I need to send prompt every time for a same task?

Langchain opens up a lot of interesting possibilities in this case however if you want to optimize for token usage I’m not sure how this would help. This is because if you have the basic model without modifications you’ll allways would have to tell it what you want, LC would be a way to make the process mire streamlined but the prompt still has to be submitted each process right?

Im no LC expert so please excuse if im wrong here.