From Margin of Safety:
It is essential that investors choose discount rates as conservatively as they forecast future cash flows. At times when interest rates are unusually low, investors are likely to find very high multiples being applied to share prices. Investors who pay these high multiples are dependent on interest rates remaining low. When interest rates are unusually low, investors should be particularly reluctant to commit capital to long-term holdings unless outstanding opportunities become available.
[H/T The View from the Blue Ridge]