I filed one around a week ago and haven't heard anything yet. Does anyone know the turnaround time for these things, please?

Probably going to be a while, as they most likely have a large queue.

What is your issue?

Looks like a memory leak. Found out about this since filing the ticket. Either way, play the game for a while and it gets progressively slower to load up textures, transition and load saves, with constant crashes to the point of it being unplayable.

dxdiag report. I haven't experienced any memory leaks. Memory use stable at ~6000MB (3-4 for Fallout 4).

There are a lot of people complaining about a memory leak. All the official troubleshooting steps have been taken and my system is beyond the recommended specs but it continues to happen. Starts fine, gradually gets slower.

Frankly, a lot people don't know what they are talking about, and often blame 'memory leaks' for non-issues.

Without a dxdiag report I cannot even begin to help.

Just to be clear - because this is far from a "non-issue" - you can play for a couple of hours at best and then things start to slow down. Scripts get slower, loading times longer, textures take longer to load, game assets take longer to load (buildings, landscapes etc.), AI stops working (creature spinning in circles, NPCs stood around not moving), stability decreases, sound effects (including speech) lag by up to 20 seconds or so, icons in your settlement builder screen take an age to load, navigation through the settlement builder menu lags and as a result the game becomes completely unplayable requiring the PC to be shut down for a while before being restarted. This is not general performance issues. I've tweaked the ini, I play in boarderless Windows mode and have followed all the other official guides including updating the driver and this is the only game I suffer this with.

Update Nvidia driver

http://www.nvidia.com/download/driverResults.aspx/95559/en-us

Disable sound devices that you don't use. Them is little point to having the integrated audio (your primary), HDMI audio, and a separate Creative chipset, all active. Go into the Control Panel >> Sound. Then select unused devices and right-click, and select Disable. Make sure to set the default device too.

If you are using the Creative chipset then update the driver.

http://support.creative.com/Products/ProductDetails.aspx?catID=1&CatName=Sound+Blaster&prodID=14103&prodName=Audigy+4

You have a fairly high commit charge:

so you need to download ccleaner (or similar) to minimize the memory use before Fallout 4 starts. You might be starting to use page file.

Make sure you only have the Page File set on one storage device. Go to Control Panel >> System >> Advanced system settings >> Performance (settings) >> Advanced (tab) >> Under Virtual Memory, click the Change button. Set so only one volume has a 'System managed' page file. Make sure to click the set button before closing the window and click Apply on the previous window.

Also, if you haven't already, make sure Shadow Distance and Godray quality is no higher than Medium.

Yeah, that's the thing about page files, Windows 10 has completely redesigned the control panel and I have no bloody clue where any of that is.

right-click on the start menu icon, the menu lists the 'Control Panel' among other stuff.