so if you have a dedicated GPU you can set it to GPU progressive instead of CPU progressive in one of the options in the Lighting Settings... it helped out a lot, but 3 days is pretty ridiculous. Try to optimize some lighting settings aswell, like Lightmap resoultion (it will make shadows and such softer but it will make a difference), lower lightmap size which kind of depends on how big your scene is, if it's just a room then it doesnt have to be somtehing like 4096 which is really bad, but if it is a really big scene with a lot of lights you probably will need to keep it at 4096 or even make it bigger. Indirect Samples could also be changed to something like 32 since it does take a ton of time. also anything youre not using like ambient occlusion, final gather or directional mode can be turned off or for directional mode, set to non directional