In regards to multiple personality syndrome is it possible that an alternate can remain in control for a week or longer?

Multiple personality syndrome, now known as dissociative identity disorder (DID), is a controversial diagnosis and not widely accepted within the medical community. Although it is believed that alters, or alternate personalities, can control a person's behavior and thoughts for varying lengths of time, it is highly unlikely for an alter to remain in control for an entire week or longer. Most switches between alters occur within a matter of minutes to hours.