Can my parents re-visit US in less than 6 months of departure from US?

  1. Currently my parents will stay here for 6 months

  2. Can them come to stay for another 6 months immediately after they return to our home country? May be after 1 or 2 months?

  3. As there is no restriction on re-entry with a Mutiple Entry visa, will USCIS r immigration have any issue if they re-visit in 1 or 2 months?