For best results Laser Skin Tightening can be done 2 weeks apart if it's with a Q switch modality.The skin needs a break, doing it twice a week would not be beneficial.
I don't know of any studies on this question, but my opinion is that once per week is the most frequent that RF should be performed with the Accent XL. Most protocols are every other week, but I have put patients on a weekly protocol with good results.