The eruption in El Hierro volcano continues with on and off rhythmic at the moment. So fluxuations in the harmonic tremor plots can be rather huge. That is from considerable amount of tremors down to no harmonic tremors at all.
The harmonic tremor in El Hierro volcano. Copyright of this picture belongs to IGN (Instituto Geográfico Nacional).
Here is also an video of the eruption in El Hierro volcano. I do believe that this pictures are rather new. But I am not sure. The audio is Spanish.
It is impossible to know for how long El Hierro volcano is going to keep up the current eruption pattern. But this pattern might stop at any time, without any warning at all.