Don't forget that the planning has to be reasonable, too. Don't assume a 100 kt tailwind on all eastbound legs. Also, you referenced "flight time." If fltplan.com generated 7.5 hrs of flight time and you're going to have to factor in the taxi time because the "flight time" you are limited by is block time. Going in/out of LGA can mess-up that plan. From 14 CFR 1.1:
Flight time means:
(1) Pilot time that commences when an aircraft moves under its own power for the purpose of flight and ends when the aircraft comes to rest after landing;
Also, here's the link to the Chief Counsel's office LOI search:
Http://www.faa.gov/about/office_org/...terpretations/