Crisitunity makes a good - and largely overlooked - point about Sarah Palin's sticktoitiveness:
Sarah Palin did have a job in between being mayor of Wasilla and Alaska Governor: she was chair of Frank Murkowski's Oil and Gas Commission. How long was she on this Commission? Less than a year... until she quit in January 2004 with a big public huff (leaving the Commission in the lurch with only one member), saying "the experience was taking the 'oomph' out of her passion for government service and she decided to quit rather than becoming bitter." She publicly cited her frustration with being unable to be all straight-talky and mavericky about the corruption and backbiting on the Commission, but the resignation also came at a very convenient time for switching over to lay the groundwork for her successful 2006 gubernatorial run.
Don't forget that she also quit four different colleges en route to getting a degree in journalism. It seems that the one lesson Sarah Palin's learned her whole life is that quitters always win.