144 hours and counting to import project

I have a very large project (previously shipped title on PC, PS4, XBox One), which we are looking at bringing to mobile. So far its taken 144 hours to import the project from scratch and it's still not done. The problem seems to be that after processing 5-15 files, Unity hangs for several minutes doing some kind of cleanup after which it spews out a message. Here's a sample message from the log:

Unloading 147 unused Assets to reduce memory usage. Loaded Objects now: 4615.

This is the case regardless of file type eg dds, wav, fbx etc.
Note that "Compress Assets on Import" is turned off.
Typical physical memory usage is 3.5GB of 8GB total.
There are 171,000 files in my Assets folder including meta files.
Restarting Unity doesn't help.
Unity 5.3.1f1 (64-bit), Windows 7, MacBook Pro (Bootcamp), 8GB Memory

Does anyone have a known solution or workaround?

 

Targeting PC at the moment. All textures were converted to dds before importing and additionally "Compress Assets on Import" is turned off, so texture conversion should not be the issue. Also happens while importing wav, fbx etc.

 

No errors or scripts running. The problem is not the time it takes to import each asset. This occurs relatively quickly as observed in the progress bar. The problem is the large repeated stalls that happen after processing every few assets, while Unity does some kind of memory cleanup. When the stalls occur the following messages appear:

System memory in use before: 243.1 MB.
System memory in use after: 243.5 MB.
Unloading 0 unused Assets to reduce memory usage. Loaded Objects now: 4606.

 

So $4000 dollars later and a new Macbook Pro with 16Gig RAM, I was finally able to import the project in 24 hours. Seems like 8Gig RAM is not sufficient to import a larger project. Note to UNITY DEVS: Please have someone take a close look at memory management during the import process. There's something terribly wrong going on there.