As a general rule I would agree with Robert, however, here in Texas, we have had lenders that have not been clear in what they wanted.  Since I used to work as a Title Examiner for a title insurance company, I usually go back 25 to 40 years.  I use as the start date the execution date of the first instrument that I had found in the chain.  Even with the start date I have had lenders come back and request a 13 month chain of title even though I had provided a run sheet for 25-40 years back to the certification date that the County Clerk had when I had finished the search.  So I have always include the time period that my searches covered.