You can use a single GI cache for an entire sequence if you wish. It is a setting in the GI Cache blend mode selection, "One File (Exact Filename)". However cloud shading will still have to be recalculated per-frame, and if you are using v3 clouds (e.g. "Easy Clouds"), the GI is not cached anyway, as the GI cache only supports environment, atmosphere, and v2 cloud GI at present. So using a cache would be advised (for any animation), and it will ensure more stable lighting, but won't improve render time. I'm not sure if that was your hope.
- Oshyan