It is talking about a military campaign that would last years, not months.

They are supposed to last at least three years (some actually do).

At times the term of office lasted two or three years.

Many companies see such terms as too steep a price for a deal that might last only two or three years.

Their marriage lasted until his death nearly 50 years later.

"I lasted three years and six weeks, which is a lot longer than many thought."

The free course of studies lasted three years, the students providing for their own support.

To last 15, 16, 17 years in the league, what can I complain about?

But his Met career lasted only two years, cut short by internal politics.

A good down pillow should last a dozen years or more.