1. If you manage your subscribers with data extensions, you generally cannot take advantage of profile attributes unless you perform an import into both your Subscriber data extension and your All Subscribers List.
2. Import Performance results vary greatly between Data Extensions and All Subscribers. Consult your Professional Services and Implementation Team or your account representative for best practices around importing large quantities of subscribers into All Subscribers.
3. Double imports work best when you can identify only delta subscribers.
4. New profile attributes added to an email account do not immediately appear in Audience Builder. Contact your Marketing Cloud account representative and ask to reload your profile attributes into Audience Builder. This procedure typically takes a couple of days to perform.