Myself, I'd prefer not to know until after the series. There's less chance of the figures themselves 'tainting' the outcome. Maybe if someone is seen as a long way behind in the figures, people will not bother to vote for her at all, or conversely, maybe they'd over-compensate the following week, rather than judging on her actual performance.
Maybe you could put a per-phone limit on it, but I don't think that would make a big difference. I imagine all the girls have relatives and friends (and certain fans) who will do multiple votes, but they will also pick up individual votes from the wider public. I'm sure it all evens out in the end.