Is there any time limit for this 72 hours free transit?

Let's say I have a flight on March 1st from Italy to Shanghai via Denmark. I apply for the visa and stay in Shanghai only for 1 day. Then the day after I have another flight from Shanghai to Tokyo. After 2 weeks in Japan, I have a flight back to Italy via Shanghai. Can I apply again for the 72 hours free tranist after just 2-3 weeks and visit again Shanghai?
Thanks.