Large hi-resolution images and memory limits

I am doing arch-viz animations. The usual setup is that camera moves into a room, looks around (with narration) and moves to another rooms etc. A five minute render can take weeks to render!

I’ve tried just about every technique (baking textures, etc) to cut down render times. Some help but are just too much work & unreliable or slow.

The technique appears to be making every room into a hdr background. So when the camera is in a room it is actually an empty blender scene with nothing exept a full 360 degree hdr background rendered previously.
Now the render times a ridiculously short (1 sec at most) and thus I can look around with static tripod-set camera as much I want. I does not matter how much stuff is in the room/area.

In above setup the only lengthy render times are when camera is moving to another room (and I am rendering a regular scene) but that I can manage.

Unfortunately the hrd images need to be huge. If my typical camera is 1024x768 for a sharp looking hdr that encompasses the whole room must be 10,000x10,000 pixels or higher. Currently my computers choke lower than that resolution.

My question is that how much memory should my computer have or are there workaround (baking is too way much work, I’ve tried that). And has anyone with lot’s of memory managed to render that hi-rez images.

You’d probably do better to post this in a different forum.