There are good reasons for changes in the flavor of a blend relating to sourcing, where the tobaccos are sourced, in which year, and how the seasons are there, and how the leaf has been cured and aged. However, a complete change of recipe is another matter, and that, I think, requires a different name for the blend. The more arbitrary the recipes of a named blend, the less meaning it has. You can fool the customer once, maybe twice, but after that, they go looking for a different blend in a different brand.