They comment about this at the end of the paper: "As of the writing of this article we are maintaining the first sample of the first element in the form of solid metallic hydrogen at liquid nitrogen temperature in a cryostat. This valuable sample may survive warming to room temperature and the DAC could be extracted from the cryostat for greatly enhanced observation and further study. Another possibility is to cool to liquid helium temperatures and slowly release the load to see if SMH is metastable. An important future measurement is to study this metal for high temperature superconductivity."

Out of curiosity, what made you ask this? Is there something about Hydrogen that would elicit such a question, or is that just a question that should be asked of any new material?

As I said, I'm genuinely curious. I'm not even an amateur here, but I wouldn't have thought to ask this at all.