Imagine two people each have $40,000. One locks it all for four years. The other splits it into four lots of $10,000, ending after one, two, three, and four years. If rates rise next year, only the second person can move part of the money without breaking a long agreement.
That second approach is often called a ladder. It is simply a way of spreading end dates so you are not locked into one decision.
Keep it simple enough to manage
Four or five amounts is usually enough. Write down each end date and set a reminder a couple of weeks beforehand. Decide in advance whether maturing money will be spent, kept available, or fixed again.
When not to do this
If you need all the money on one known date, match that date instead. If the money is your emergency fund, keep it easy to access. If the total is small, do not create lots of tiny accounts for a tiny gain.
Each time a piece matures, look at today’s rates before you renew. Automatic renewal of everything recreates the original problem.