Players may pay a Story Token to use the same Power more than once a Page or a Blocking Ability more than once a Scene per incidence.

My knee jerk reaction is that it will hardly ever be used, in comparison to using a story token for another action, laying another conflict, getting a new character, etc.  But I'm not really sure what is prompting you to suggest this rule, so I can't say for certain.

Mainly it was to benefit Mundane characters and allow them a bit more endurance in longer scenes. 

I see.  I suggest to you that one of the interesting effects of the limitation of one use per non-powered (and to a lesser extent one power use per page) is that it makes players think very carefully about when to actually use their characters in a scene.  It's like a kind of moral hazard built into the game; use your stuff frivolously and you risk getting stuck with nothing left to use when it matters later on (or being forced to gain debt when you really don't want to).

I also find the limits are a great spur to cleverness.  You want to roll THAT dice.  The only thing you have left to roll it with is THIS ability.  Can you come up with a clever narration that ties THAT to THIS, that won't make your friends throw popcorn at you?

That being said, at the cost of a story token per, I would have to be pretty desperate to reuse something.  So I suspect that this change would not really make a big difference.  You would have to play test to be sure.