Reaching out for some advice...
In November I bought a new build with a 3090 FTW3 and the display via displayport would intermittently flicker black whilst both idle (desktop) or under load.
This lead to RLOD within 9 days and it had to be replaced.
The replacement worked flawlessly until 3 days ago (so about 3 months) when it started presenting the same issues.

Monitoring via GPU-z shows that when the primary display (on display port) flickers black the GPU reports a sudden drop in memory load and power draw followed by a spike in power draw, yet the second display connected via HDMI remains fine.
At the moment I've resolved the issue by changing the global power management of the card to maximum performance.
This is a worry for myself as some of the other 3090 users doing this had their issues resolved whereas others reported back that the card died 2-5weeks later.

Nothing about my system has changed between the card working properly and now.

RMA for the 2nd time ?

(Thank you for your time)

LiBraga
Reaching out for some advice...
In November I bought a new build with a 3090 FTW3 and the display via displayport would intermittently flicker black whilst both idle (desktop) or under load.
This lead to RLOD within 9 days and it had to be replaced.
The replacement worked flawlessly until 3 days ago (so about 3 months) when it started presenting the same issues.

Monitoring via GPU-z shows that when the primary display (on display port) flickers black the GPU reports a sudden drop in memory load and power draw followed by a spike in power draw, yet the second display connected via HDMI remains fine.
At the moment I've resolved the issue by changing the global power management of the card to maximum performance.
This is a worry for myself as some of the other 3090 users doing this had their issues resolved whereas others reported back that the card died 2-5weeks later.

Nothing about my system has changed between the card working properly and now.

RMA for the 2nd time ?

(Thank you for your time)

Can you give us a list of your system specs.  I'm wondering if it has anything to with the PSU or unfortunately GPU.

Make sure your cables aren't loose and everything is where it should be. 

Also, check to see if your GPU drivers are up to date as some have had issues with flickering in the past.

LiBraga
Thanks for the responses...

I've tried reseating and checking cables.

System Specs :-
CPU : Ryzen 9 5950x
MB : Asus ROG Strix X570-F Gaming
PSU : Corsair RM850x
GPU : EVGA RTX 3090 FTW3 Ultra (V2) - Currently on Driver v496.76
Display 1 : Gigabyte M28U (4K, 144Hz, HDR disabled both on monitor and in windows due to streaming)

To recap, this system had worked perfectly for 3 months with the nvidia power management set to normal.
It works fine with the global nvidia power management set to prefer maximum performance.

My concern is that this is the beginning of hardware degradation and it will eventually RLOD like the last one.

Thanks for the details.

Are you running any APC/UPS backups to the system?
 
Worst case, you run into the inconvenience of RMAing again but hope it isn't your GPU.  I don't think it is just because it happened before.  Flickering can happen for many other reasons as well.  Windows updates, uncertified cable, etc.

I get flickers here and there when I browse on the web.  Been happening to me for a few years now.  It's still kicking strong after 8 years. lol

LiBraga
Unfortunately I don't have it on a UPS atm.

I will clarify though... the flicker is more like the screen turning black for 3s.  Sometimes it would happen once an hour, sometimes 3 times a minute.

Did you by any chance update the drivers since these issues arised?  Either way, try rolling back a driver or two to test it out and see if the flickering stops.

I have three of the FTW3 Ultra cards.  The very first one I had to RMA within a few weeks as it simply died.  Funny thing, the only time I see that flicker is when Nvidia releases new drivers and they are installing.  Just like you describe.
And my cards are run 24/7 mining.  I have a fourth card as well, another 3090 that is a Dell Alienware model.  Not nearly as performance oriented and is constantly running lower hash rates, though it does consume 50 watts less power. 
All 4 are installed in my 2 rig Lian Li desk case.  It's hot in there too, having to replace my fans to get temps down below 80C