It's nothing new. People have always changed jobs. And people who change every two years end up with 50% better salaries over time. If you haven't added enough value in those two years to make it worth hiring you in the first place, then you probably weren't a great hire in the first place.
180 days of sumero-akkadian cuneiform, in which I find out stuff about ancient clay tablets, write about it, and ponder on whether the next 180 days should be spent on something more useful...