Another string-related question

So, I normally play in DAD, but I'm studying Jessica Comeau's book, and the songs I'm working on are mostly CGC.  Is it better to leave the strings in CGC and tune up to DAD when I need it, or is the opposite better?  I'm thinking in terms of keeping the strings from getting floppy from being DAD and coming down to CGC.  Or does it even matter?  Is the answer different for fresh strings compared to strings that have had some playing?  

Thanks!

Lisa