While Dream Heights hasn't been a stranger to publicity since its launch a few weeks ago, this latest update doesn't require you to play the game for any long stretch of time; just play the game long enough to connect your Dream Heights account to your Facebook account and you'll be eligible for your prize. To be technical, this in-game promotion (detailed in FarmVille Express) doesn't specify that you'll need to reach any particular level in Dream Heights, so I'd just play for a few minutes and then start to check back on FarmVIlle to see if your rewards have arrived.
If this is anything like the Dream Zoo promotion, you might need to wait 30 minutes to even more than an hour for your Unwithers to arrive, so don't panic if they don't show up immediately. Good luck on receiving yours!
What do you think of this cross-promotion? Will you play Dream Heights for the free items in FarmVille? Sound off in the comments.