Question about parents B2 visa extension and re-entry

My parents came to US earlier this year, and applied B2 extension which is likely to be approved, but they need to go back to China to take care of something during the B2-extension time. Their plan is to come back to US one month before the expiration date of their visa extension, then they will get another 6 month after re-entry at the Customs.

My question is if anyone has experience doing this? Do you think this would have any impact on their future visa application?