Nope, nothing wrong with stopping at 6 since we have 2 more coming tomorrow! Definitely would be a mistake to level another right now.
I’ve got mine higher than usually, because I see light at the end of the tunnel. My Shere Kahn and Queen are ready to level to 10 and Toy Alien is at level 9, so when the event is over I'll only have Alien and the Snow White characters that will need leveling. If I can work it out right, and they give us more of a breather between events, I have a small chance of max leveling ALL MY CHARACTERS before the next event! Is their any real advantage to doing that? No, but I’d love to be able to say I did. Worse case senario, I should be down to just the Evil Queen and possibly Grumpy, by the time the next event starts!