The web site for Mosquito Barrier says:
Just one spraying of all natural, liquid garlic-based Mosquito Barrier will keep mosquitoes out of your yard and away from your home, 24 hours a day for nearly a month.
Since this isn't nearly as concentrated as the commercial stuff I would think you could expect a week or so, as long as it doesn't rain.
Thats amazing. This may be the most useful post I've come across yet. Thank you.
Im outta here. I gotta go find the sprayer.