I've been buying I bonds for a few years now, mostly through TreasuryDirect. I've read of various ways of "laddering" bond purchases. My bonds are my emergency fund at this point, soon to be part of my retirement plan.

 Does anyone have any pointers to offer when buying treasuries?

IBonds and other savings bonds are unique in that they have a fixed principal and variable maturity. You can redeem them anytime after one year, after five years without the three month interest penalty, and after thirty years, they stop earning interest.

With IBonds you can purchase whenever you have a need in your portfolio and the fixed rate appears favorable. You can always redeem them later if the current fixed rates are higher. Also, you can redeem them in a manner to manage your tax liability in any given year.

The purpose of laddering is to allow you to have a percentage of your fixed maturity securities (Bills, Notes, and Bonds) mature each year. With a laddering of say five year notes, you could buy 20% of your allocation each year and rollover that amount each time it matured With the reduction of the minimum purchase amount to $100, you could easily buy monthly even for small portfolios.

With the exception of IBonds, you are really better off buying treasuries in retirement accounts. Only some custodians allow treasury purchases at auction without charge.

I'm not sure the concept of "laddering" really applies to I-bonds.  Laddering is applied to fixed income securities because of differing maturities and differing yields.  

 In an I-bond, the yield is variable (according to the government's definition of inflation, which is less than most of us seem to "feel") and the inflation component is the same  for all bonds no matter when you bought them.  Yes, the fixed component is different and adjusted every six months, but that doesn't really help in a "ladder" because these are fairly open-ended maturities (at least up to 30 years, I think).

You could do laddering with TIPS -- the bonds themselves, not funds or ETFs -- because they *do* have different, fixed maturities and that's where bond laddering works.

I plan to hold my I-bonds for a long time.  I purchased about $4,000 face in 2000 when the fixed component was at 3.4%.  Unfortunately $4K was all I could scrape up back then, because a safe, tax-deferred 3.4% over inflation seems like a heck of a good deal today.