Research scientist and field scientists rack up miles galore to exciting places like kwajelein, dutch harbor, homer, san diego and the panama canal. I reckon some of the scientists I work with go on at least two international meetings a year and three trips to conferences around the US. Put in at least one mid-atlantic ridge or pacific cruise and you have gotten lots of field samples, a nice tan and some miles.
You can't keep your govt accrued miles for personal use, but you can use those miles for travel to conferences etc.
I haven't had to fly anywhere more exciting than DC, San Diego or Dutch Harbor in a long time....for work that is.
However, my crankiness due to lack of overhead space when I boarded Alaska Airlines flights got me my first MVP status (lots of trips to Alaska that year) and started me on my way...