I found this on Knott's Haunt sight. I wasn't sure myself:
New for 2013, Fright Lane with Skeleton Key allows you to bypass the regular lines for 11 mazes as many times as you want all night long. The Skeleton Key (included with all Fright Lane passes) unlocks additional rooms and interactive scares in select mazes. Purchase soon, as this popular offering is expected to sell out!
So I think the Fright Lane is unlimited, but I'd bet the Skeleton Key is limited.
Last year they would punch out card/badge at every maze we used it on. They punched it on the name of the maze. Unless they changed things, expect the same. This early on in the season, most mazes did not need it unless it was a headline maze.
Front of the line that comes with the MiceChat event is good for UNLIMITED front of the line at mazes. There is a separate front of the line pass that is good for the ride but not included with the event. Also, the skeleton key which is tied into the front of the line pass for the mazes unlocks extra rooms in Gunslinger's Grave, Black Magic, Endgames, Slaughterhouse and Dominion of the Damned.
Previous years had a limit of 1 per maze but this year is unlimited.