Here is yet another rally comparo — this one looking at all major market rallies of the last 109 years.
The Dow has begun a major rally 27 times over the past 109 years which equates to an average of one rally every four years — most major rallies (73%) resulted in a gain of between 30% and 150% (29.8% to 150.5% to be exact) and lasted between 200 and 800 trading days (9.5 months to 3.2 years):
courtesy of Chart of the Day
I think a more informative chart would look at bear market rallies, rather thasn include secular bull markets. It skews the run towards the longer time line.