A 68-year-old who has only 36% in bonds asked what to do: buy more bonds now or wait. Syndicated columnist and author Scott Burns suggests waiting in a 3-year ladder.

"So you needn't be in a hurry to increase that allocation to 60 percent.

If you do start increasing the allocation, the safest way would be to build a simple three-year ladder."

Scott Burns: What to do about bonds