I've had names in this category for quite a while (chemicals/paints) but have never sold one or had much incoming interest in any.
It is like any name we hold, all it takes is one person wanting a particular name for the situation to go well. In the chem world, contacts tend to be more cerebral and less 'marketing' based so old fashioned sales techniques have not returned results for me.
However, I will continue to buy and hold in this category and pick up more as 'near top tier' or 'top tier' names become available.