I guess the trade off to having all your miles go into your primary account is that you would have more miles to use for anytime awards. My main airline is AA, and it's filled with non-flying miles - probably more than in flight miles. Of course, because AA allows for lifetime status, there is an incentive to have EVERYTHING I can go there. Once I reach lifetime Platinum I will think some of this differently.
------------------
Ms.DtG