Are volcanoes at converging plate margins always active?

I ask this in the context of magma production. If the plates are meeting, sinking and magma is being formed under the earths crust due to the laws of physics which state that matter is never lost but converted from one state to another. Rock is thus converted to magma. So now please tell me with reasons whether or not volcanoes (which are btw defined as openings to the magma levels) at such plate boundaries are always active.