As a mod elsewhere - If you can't spend the time flagging, editing, and otherwise helping make the site better now, you're not going to find the time to moderate.
One of the funny things about being a mod is, how little I actually need my mod powers. It speeds things up. I have a flag queue for users to let me know about things that need my attention. But there's not that drastic a difference between a 30K user who's using his powers cause he cares and a mod.
But still I do not want to run for a position that is consuming too much of time
Run for the position cause you care enough to spend that time, and would spend it anyway on the site.
So, if you were a mod, how long do you think is worth spending on keeping the site awesome?
Its not just about time though. Its about coverage. Moderation dosen't typically need a good chunk of time unless its something complex - voting rings for example. It does need consistency. I've basically popped in and handled flags over lunch and on my way to and from work during my last job and it worked great.
If you can pop in for 5 minutes, and skim the mod queue, and its usually enough.
You also are probably going to want to pop into meta every so often. Maybe once or twice a day, skim through posts, answer things.
Not all mods do this, but I'm typically contactable over chat. Once again, I'm on chat anyway and I rarely need to put on my mod hat and help moderate stuff.
I'd be doing these anyway, and spending about the same amount of time. I'm on another site's meta, answering this arn't I?