再細問一個問題

Regarding "Always stay out of US longer than in US before applying another visa," here's the scenario:
My parents' first visit: 06/2007~11/2007 (roughly 5 months)
My parents' second visit (suppose they use the same multi-entry 1-year visa): 3/2008~6/2008 (3 months)

When is the earliest time they can apply for their next visa? Is it around 03/2009 or 06/2009?

Thank you again for sharing your knowledge! It took my parents 7~8 years (more than 10 denied visa applications) to finally get their first visa. I just want to spend more time with them if possible. I won't be naturalized until 2011 at the earliest.