Why is it that calcium channel blockers dont have to be used forever in most cases?

I am a 21 year old male diagnosed with heart palpitations.  my heart doesnt race BUT it does beat hard enough for me to feel it from time to time.  i was prescribed cardizem la.

my cardiologist told me that since my echocardiogram was normal, i should only have to take this medicine for 3-6 months.  he said that is usually what he encounters.

why is this?  what is the science behind this? do the calcium channel blockers re-train the heart to not use as much calcium so that it doesnt beat as forcefully?  thus removing the palpitations?

i still have palpitations from time to time...which makes me think perhaps my dosage should be slightly higher?