Here's a little "Pro-tip" to all you young, stary eyed roleplayers out there. ((All of us cynical, twisted ones already know this sort of thing.))
If you don't have the time to play an important role in an active game: DON'T APPLY FOR IT.
Seriously I shouldn't even have to explain why this is a terrible idea. I mean, who doesn't want to have a chance at being important to the plot and story at large. In our dark twisted little hearts, we'd all love our chance to shine for a little while, but at the same time, if you know you're not going to be able to keep up, if you know beyond the shadow of a doubt that things are about to get crazy, not once but over and over and over again... think carefully about taking on anything that requires in game responsibility.
Not only does it hurt the game at large if you can't be there to play your lynchpin role, but it will also hurt it if you promise to do things by a deadline, and then push it off... and push it off... and push it off...
The mature thing to do at this point, if you have found yourself in such a role, would be to speak to one of the moderators or storytellers and explain your problem, and see if they can -take the role off your hands- so that you're not holding things up. Especially if the story is bopping right along otherwise, and people are anxiously waiting to see what you'll do.
The immature, not so classy thing to do is sit back, make a bunch more characters, and go fish around for them to get roles that are, if not AS important, still pretty important, and ignore the character that's lynchpin for a certain role.
If you do the second option, and you do this for... oh... six months or so, especially if you do this while RPing with others of your characters and chattering cheerfully away, please don't be excessively surprised if other people become strangely angry with you. I mean, again, do I really have to say why it's unreasonable not to expect people to be frustrated at this juncture?
And if on top of all of that, when finally confronted by the fact that you haven't done more than wave your hand vaguely at the things you promised to do when you took on the role, that you, personally, agreed that you would do...
Please please for the love of god don't throw a tantrum about how it's your Motherfarking birthday and it's not fair to call you on it that day.