Your bonds are spread out so that some money comes back every year. Here is why that matters.
Your bonds are spread across 2 to 7 years, like rungs on a ladder. Each year one rung is repaid to you in full. So some of your money comes back to you every single year.
When a bond is repaid, you buy a new one at today's interest rate. If living costs rise, interest rates usually rise too. So your income catches up over time.
A long bond pays the same coupon for 20 years, even if costs rise. A ladder lets your income step up as each rung is replaced. That is the difference between standing still and keeping pace.
No more than two bonds from any one bank. No more than two bonds coming due in any one year. That way no single bank, and no single year, matters too much.