Jerry I don't think that there is an exact amount of time to keep them in the fridge although someone here just might do such an experiment at some time. It would be interesting to see what the optimum time would be, if there is such a thing. I've taken cuttings in the summer here in Louisiana, put them directly in a pot of potting soil in the shade of my house and they grew beautifully. The ones I'm rooting in my "first rooting experiment" (see the post) stayed in the fridge about 2 weeks. The only reason I removed them and got started was the fact that part of the paper towel had frozen and there were some ice crystals on the cuttings. So watch them to see that they don't freeze, and then that might not be a bad thing either. Who knows.
When I did mine I wrapped them 3 or 4 to a loose bunch and had them completely enclosed within the paper towel and sealed in a baggie. Remember a fridge can extract a lot of moisture so be sure it's sealed.
I'm sure others will chime in with great info, I'm just a newbie myself. Good luck with your attempt and keep us posted so we can learn along with you.