We have no intention of drawing on the funds, both IRA and taxable for another 5 years, so we do not have a need for the cash flow at this time. Further, the rest of the portfolios generate a significant amount of annual cash flow, so bottom line continues growing.
I do like the zeroes with the higher yields, and the insurance on the Forney, TX issues provides some additional comfort with the maturity dates being so far in the future. Before I bought the first ones, beyond their offering statements, I dug deep in to the economy and liked what I saw...good location, Amazon building a new facility, etc. Since then S&P did upgrade their credit rating, so that was nice to see, as it validated my research.
I think most investors shy away from the zeroes because they want the cash now, and so that leads to the higher yields with less demand for them. Certainly there is some additional risk in not receiving the cash along the way in that I'm banking it all on the payoff at maturity date. But again, the insurance mitigates some of that risk and I'm good with laddering them to produce cash flow in the maturity years.
Overall these represent 10% of our current portfolio value (at original purchase prices) - roughly 3 years worth of the cash flow the rest of the portfolio is currently throwing off.