History shows that "out of sight is out of mind".  With the address "Valid Dates: Date from" on a separate screen from bio 1(using the "More" button) , most folks don't think to go there and fix the "date from" on the new preferred address after copying to alternate. The now alternate address "Date to" is automatically set to current date.  Logic says why not do the same for the "Date from" on the new preferred address.  If not accurate, it is difficult to discern the chronological moves of a constituent from address to address over time.  When keeping historical addresses, this is helpful information to know when doing prospect research.