cash back is a terrible use of points / miles, I would much rather prefer to gift it to my friends or family members to get full redemption. But also remember 200k miles isn't much considering it can cost 65k for a saver award to go across the world just for yourself, if you go with a spouse it'll be 130k miles leaving you with not too much. I think after 400k I would start to think about how to use rest of the miles =)