On a system that meets the recommended hardware spec, it's currently about 15-20 minutes for an 8k map. Maybe 25 minutes at the bottom end of the scale.
If it's taking you that long, then the client is unable to use your GPU for map generation because it does not meet the recommended spec. As a result, it must rely on your CPU. Since your GPU isn't up to spec for the job, it's typically not very likely that your CPU is either, and then there's the fact that you also don't likely have enough RAM, so it has to additionally switch to using your pagefile on your archaic platter drive instead.
Basically, if you aren't on the recommended hardware, your PC keeps kicking itself in the ass until everything can only take forever.