I don't have experience with GCA. My Dr. had originally told me to take my dose all at once in the morning. His reason was because it could effect my sleep if I took it at night. The trouble was if I took it all in the morning it would wear off during my sleep and then I be awake, in pain, and had already taken my daily dose. I've since split my dose and take half in the morning and half before bed. It's working very well for me.
I would speak with your Dr and ask why it needs to be taken all at once. I believe that's the general recommendation but every person/situation needs to be evaluated for what works best.