As far as magic goes, in fantasy fiction, is less actually more? I’ve been mulling this over lately, apropos a thread at the Black Gate forum (starting about here).
On the one hand, I think a magic-intensive narrative faces the challenge of diminishing returns. If antagonists are throwing mountains at each other on page one, throwing pairs of mountains on page two will not have double the effect, likewise trios of mountains on p. 3 etc. Also, it’s likely to turn away a large amount of the potential audience as being too remote from reality to believe. This is dicier, though. The readers of Snergartholept: The Little Magazine of Big Weirdness are less likely to be alienated by freakish displays of magic than subscribers of Dulles Quarterly: The Magazine of International Policy and Missionary Somnolence.
But after all: are fantasists really trying to snatch readers from Dulles Quarterly: Where Interesting Information Goes to Die a Long Tedious Death Among Hypotactic Clause Structures? Probably not. They are (or may be) competing for readers of Snergartholept, starting with the editors. If these guys expect a little mountain throwing, you might want to try some on page 1, assuming you can justify and sustain it. Then it becomes a question of how you do it when you do it, not whether you should ever do it.
To self-plagiarize something I once wrote in another context: sometimes less is more. But sometimes only more is more.