Oh... and here's a good way to keep the comic going. Keep big antagonist's hidden 'till the end. Make villains as interesting as the good guys. Have a plot that continues on, like problems that continue on until they are solved, and/or certain things being brought up again. And finally, and most importantly, WHEN the big antagonist shows up, make them either-
A. Make them kill off a important character.
B. Make them able to be just as interesting as villains, and/or be insanely powerful (like a powerful attack that's shown in the past that destroys ships, does nothing to him).