#1, it's not too late; in fact, they could send him back at any point during the season.
#2, the ten-game limit that everyone talks about is only a contract thing. They'd have to send him back before he plays in ten to avoid the first year of his contract from kicking in. If they do, his contract would begin next season.
Fleury has played in eight, which hasn't affected anything yet, but Craig Patrick said that he'll keep Fleury up for a while, well past the ten-game mark. The Pens could benefit by sending him back after his contract kicks in but before he qualifies for his bonuses -- that way, the Pens would only have to pay his base salary.