Hi Kevin
what material did you try it on and what did you think on the finished look of the product. If this product did offer the longevity of an impregnating sealer, would the initial application costs out weight the cost of stripping and resealing a topical sealer periodically, when a customer wants shiny slate.
Cost wise the product is around £60 per litre, but with discount direct from Fila (45%) you could pick this up for about £35/£40 per litre. The coverage is 10/20sq m per litre on stone.
Out of interest is your new permanent solution a mechanical shine or a product you apply or are you keeping it under wraps for now