I like that smart lists are volitle and always changing with the database; however there are also times where I need to freeze the data to know what it was at that point in time. For instance, I'm queing an email and I ran a smart list to ensure that none of them were getting my nurture campaign. I'd like to freeze the data now to reassure myself, or other colleagues that it was right at the time. Now, the ability to un-freeze it and have it re-calculate again is also beneficial. Another option would be to include a history of freeze points to create a library of sorts to know 'when frozen on XX date, it was XYZ' or 'when forozen on XX date it was ABC'