We took about 15 months to plan (still planning...two weeks and counting), but we certainly didn't need all that time. We just took it 'cause we could. I think a wedding with all the bells and whistles can be planned in 6-8 months. Most of the time, the reason you need a larger window is because in some places, reception halls, bands and photographers book up to a year in advance.
We're having a non-denominational ceremony. Our college professor is going to officiate. We ordinained him through the
Universal Life Church. You'll have to check the local laws where you're getting married to see if a ULC ordination is acceptable. Ours is acceptable in New York State, but if we were getting married in the city proper, we wouldn't be able to have him do it.