NFCU offers addon CDs such that you buy a CD that has a 3 year maturity, yielding the commensurately higher rate for a longer maturity CD, and they allow you to add onto it with new money at any time.

It seems like a ladder could be created. Every 6 months you buy another 3 to 5 year CD. And as you get within 6 months maturity, you buy into it and get the 3 to 5 year rate, even though you’re only locking in that marginal money for 6 months.

Hypothetical examples here with made up numbers:

12 month CD rate = 2%

24 month CD rate = 2.5%

36 month CD rate = 3%

48 month CD rate = 3.5%

At time zero you buy the minimum amount ($1,000) to open a 48 month 3.5% CD. This is CD 1.

In 6 months you buy another 48 month CD at 3.5% at minimum amount ($1,000). This is CD 2.

Repeat until you have 8 different CDs, each maturity at 6 month intervals over the course of 4 years.

Whenever you have excess cash to stock away, you drop it into the 48-month CD that’s maturing soonest, which will always be 6 or less months. But you get the return of a higher risk, longer duration CD.

When your CD expires, you use the proceeds such that you put the minimum amount ($1,000) into a new 4 year CD and put any excess into the next CD in the ladder that’s expiring within 6 months.

You could do this every 3 months, assuming you have the money for the minimum CD amount to cover that. At $1,000 minimum per CD a 3-month laddering of 4 year CDs would be $12k. Easily doable for most savers that would even consider an advanced technique like this. Albeit more overhead in effort. 3 months seems reasonable so that might be the sweet spot for me.

Seems like free money on a risk-reward matrix. The biggest downside is that it takes a few years to get rolling.