I was wondering how long I should circuit train to get lean but to not lose too much muscle m.?

I'm currently a pretty fit person right now. I lift weights regularly and I'm at about 12% body fat. I'm going to be taking a vacation in about 4 months and wanted to appear as ripped as I could. In the past I've used circuit training to get really lean. I wanted to start circuit training before my vacation but I don't want to do it for so long that I start to lose muscle m. I was wondering how long I should do it before I leave on my vacation. Perhaps 2 weeks before I leave since I'm already on a workout regimen?