父母多次入境对今后签证的影响？

My parents came to the States with a multi-entry visa valid for one year. They've stayed with me for 5 months and are now going back. If they come to the States again, before their visa expires and stay for another 3 months, will that affect their next visa application in future? After they go back to China the 2nd time, how long will they have to wait to apply for a new B2 visa?

Thank you for sharing your experience!