The concern would be that these conditions, and our policies, could be encouraging irrational expectations of high returns. Is there any sign of that now? By most measures, equity valuations seem to be within a normal range.
Whether one looks at trailing or forward price-to-earnings ratios, equity risk premiums, or option prices, there is little basis for arguing that markets show excessive optimism about future returns. Of course, in the equity markets there is always downside risk.