If you have your heart set on a particular condo due to theming, location, etc., I would say the earlier the better.
We had to change our plans from onsite to offsite. I started looking at WH availibility for our upcoming summer trip 7 months in advance and was shocked to see that most of my first choices were already booked for my timeframe. Of course, if you're going during a less crowded time of the year, then it will probably not be as much of an issue.
We have friends that are going the same time we are who are now trying to find a place in WH. Most of their top choices (places with Mickey themed rooms, etc.) are already booked.
I have friends who were able to find accommodations 2 months out for a trip during spring break; however, they're not as picky with their choices.
I hope this info helps. Good luck with planning your trip.