"Foolish consistency is the hobgoblin of little minds". Harsh. But most consumers of images and art want their creators to be consistent in their styles. That is not true of the Masters. Picasso went through myriad periods, styles, manifestos, schools before moving on. Gerhard Richter equated this obsession with consistency with dying as a creator.
I have a lot of sympathy for Gallery owners, collectors and fans wanting artists to stick to a style. It helps "brand" an artist and his/her work.
I don't think it helps a creator. I think it stifles growth. Just like actors or singers to play the same role or sing the same song for a life time is a little death.
What to do? I'm sorry to say for both the artist and collector the two should part when both outgrow each other. But when they are in harmonious appreciation- what a lovely world this can be.