Ive had multifocal pvcs for 7 years. entirely normal echocardiogram, ecg 48 hour ecg and treadmill ecg. the other day had couplet pvc, is it benign?

Unlikely. Cardiac: Re-Entry (↑ed automaticity far less) is the most common known basis for premature complexes. Overwhelmingly dominant basis for re-entry is muscle cell injury, especially endocardial cells, due to ischemia. All tests you mention, also angiograms, do not show ischemia or damage until quite advanced. Atherosclerosis begins in childhood & primary drivers: lipoproteins glucose BP smoking low fat foods.