The U.S. military’s retirement system has long been a great deal, offering service members basically half of their base pay for life. But for years Pentagon budgeteers have griped that the entitlement is bleeding them dry to the degree that readiness is in jeopardy.

So, in 2018 DoD is shifting from the current retirement system — known as “high 3” because it’s calculated using the average of a service member’s highest three years of earning during his or her time on active duty — to a radical new system called “blended retirement.”

This is a big change with a lot of moving parts, and it’s not too early for military families to consider the financial matrix they’re going to have to navigate next year.

Listen to military benefits expert Tom Philpott explain the details of this new “blended” retirement plan: