The great problem with Seventh Day Adventism is that it is a false, man-made religion. It dates back only to the 19th century, puts the ridiculous ramblings of Ellen G. White on a par with scripture and practice deceptive tactics: http://millennium.fortunecity.com/lincoln/666/clearwordbible/clear-word.htm
How long they live is irrelevant.
How can celebrating the Sabbath on the seventh day of the week (aka Saturday) be false? Might check back in with the Ten Commandments.