The last time the number of months went really high was for the 12 years between January 1973 and January 1985 - January 1985 was a new high even though the real S&P500 was 1.56 (vs. 2.77 in 1973) - that's the noticeable impact from dividend re-investment.
As of April 1, 2012, it has been 139 months without a new high in this metric. To avoid breaking the 1985 record, the real value of the S&P500 would have to jump by another 12% in the next 5 months. That level of jump is obviously not outside the question (it's about the same as the jump from January 2012 to now).
Stay tuned to see if we set a new record drought or not!