I don't really think that the lanterns would necessarily be regarded as 'low risk' as the type of equipment in the document Kerry linked to is. Additional considerations in this instance might be whether the lanterns (or their cables) are likely to be knocked (or pulled) by other activities - using access equipment or moving scenery for example. These might be considerations in a performance space for example but not in a 'gallery'. The CoP also suggests that whilst record keeping is not mandatory, it is useful to see if there is any history of degradation. If the lanterns are 'tungsten', then heat degradation over time might be another issue to consider. I suspect the OP was looking for a simple answer, but sadly there really isn't one. No activity is really risk free, that would be unrealistic, but when I am making this type of decision, I always picture myself on a jury and ask myself would the precautions I did take be viewed as reasonable (or reasonably practical).