Doing a soft launch with just one of your JV partner's list to test the campaign before it goes live to the rest of the world is always a good idea. It gives you a chance to make any changes required, as well as give you an idea of the conversion numbers you can expect to see.

I'm planning one with my upcoming campaign to go 1 week before the main launch.

I'm curious to know what timelines other people use for their soft campaigns compared to their main launch.