RubberDuckyDJ
For a while my mouse was fine with no DC, but with the recent update v1.0.20 and Firmware v1.43 the DCing has started again and is quickly getting worse. Hoping for a permanent fix soon.

Having the same issue here.

Product Management is aware, and should be fixed in the next update. No ETA for when that will be available unfortunately. In the mean time, if you're having issues with the latest firmware, you can download an older one here and flash it until the next update - https://cdn.evga.com/Mice/Unleash/X15_v1.35.zip

New version of Unleash is available - https://www.evga.com/EVGA/GeneralDownloading.aspx?file=EVGA_UnleashRGB_1.0.21.0.zip
 
   1. Fix X12 / X15 / X17 Left and Right click lost if clicked at the same time.
    2. Key Assignment support combination keys.
 
Should also help with the disconnect issue, let us know if you still have issues!

EVGATech_JaesonW
New version of Unleash is available - 
 
   1. Fix X12 / X15 / X17 Left and Right click lost if clicked at the same time.
    2. Key Assignment support combination keys.
 
Should also help with the disconnect issue, let us know if you still have issues!

This definitely has not helped with the disconnect issues. If anything it make it worse. When this first started the disconnect only happened when my PC went inactive for several minutes but not my mouse disconnects while using it while gaming. 

Mine is still constantly disconnecting too. The scroll wheel still goes crazy whenever it's used.
This mouse is useless and I'm not buying a 3rd.

Thanks for the updates, we'll look into it further.

EVGATech_JaesonW
Thanks for the updates, we'll look into it further.

So a few firmware updates ago (when this first started happening) I went into the power settings and changed some of the USB options for my PC. Power Options > advanced settings > USB Settings > USB selective suspend settings >  change to disabled. 
 
I noticed that when i moved it from enabled to disabled the issue stopped and only started back up when I did a firmware update a week or two later. I assumed the update was the fix for the issue but it only broke the temporary fix I had found. It might be worth looking into if this issue is related to that setting. 

This problem is really really bugging me like hell!  please fix it ASAP!
I have bought 2 of this X15 because I liked the lay-out for my MMORPG,  all of them having this USB disconnect issue, then I RMA one back and got a third one AND still having this issue!   super annoying when your mouse stops working randomly a few times everyday!
Very please look into this issue! it has been too long for a good company to respond to such a dire issue, it certainly making me think twice buying any more EVGA product in the future.

Any news on when a fix is coming for the random disconnects? Or would it be better to stop wasting time and just use it as a target to shoot at and buy from a better company?

Accidental solution found(maybe):
So after Im trying to ease the pain of plugging unplugging USB cables several times per day I bought myself an USB hub from Amazon the thing with 4 individual push on/off buttons, and installed right next to my keyboard to plug the X15 mouse in.
 
Guess what? 2 days passed and I have no issue of disconnect!  my version is 1.0.10 and  firmware  1.45  I do not know how long will it last or does it actually fix the issue.  If you have some kind of usb hub maybe worth a try.