To my knowledge Nikon didn't fix this with a firmware update. I frequently stack ND's to 16 stops and do exposures in excess of 5 minutes. Without LENR on my D800E there are white dot's all over the image and it's a real PITA to fix in post. (I use Lightroom I Understand C1 has something to help with this) LENR is a real mood killer in the field as everything takes twice as long and with the light changing fast you can miss shots because of this. I guess this is the price we pay for the DR/Shadow recovery ability of the Sony Sensor.
Actually on later models of the D800e, Nikon did a "silent" fi. I had a early D800e and am very aware of the "white dot" problem. Even wrote about it on my site as the problem is really a PIA. The only thing that really will fix it is C1 with the single pixel noise reduction slider.
White Dot problem in D800eLater versions of the D800e had a "fix" for this as I have used several D800e cameras that were shipped after about 9 to 10 months after announcement. Nikon just fixed the problem under the covers. I attempted 3 times to have my camera fixed, but Nikon told me "non NPS, nothing we can do out of warranty"
With the D810, Amazingly, this same fix was overlooked. Nikon did recall all the early D810's again I had one of them. The fix was never fully discussed by Nikon, but it did require the camera being sent back to Nikon, so it was more than just a firmware update as a end user can apply that. Something else was added at the repair center. With the fix the D810 is very clean in long exposures at night, only showing some stuck pixels, which take on a different look than normal, instead a bit of a jagged look.
As for the A7rII, I owned one for 1 week, did, use it on long exposures in warm climates and the amount of stuck pixels was as severe as I ever have seen. Ruled out using LR altogether as LR has no fix for this. C1's single pixel noise reduction does a good job, but to you have to really apply a lot of it and that can have some effects on the image. Fred M does have a free action that may work also. I sent my Sony back for this and other reasons. Others have confirmed that the firmware fix to allow non-compressed raw does not effect this issue.
Net, the A7rII, can get hot, and once it does it creates a lot of noise. There are reports of video shooters overheating the camera in 4K mode after 15 to 20 minutes. One had the camera lock up, the other had the over heating warning show up. I have never had a camera that warns about over heating, but apparently the Sony does.
Sony's answer is use Long Exposure Noise Reduction, as it does take out the stuck pixels. I don't know if Sony spoke to many night shooters as stacking is the preferred method for this type of shoot. Stacking and LENR are not a good combination due to gapping created.
On Fred's site, many of the night shooters owned the A7r (which does have this issue with stuck pixels) or the A7II, again which is very clean on longer exposures so they dropped back to those cameras for night work.
One other note, I found my A7rII, to have too much noise in shadow recovery even at base iso, comparing that to the Nikon's I use, D800e and D810. I had expected a cleaner image at base, due to the BIS tech. The review my Michael Tapes on this site, where he compares the Sony to several other cameras confirms this also. My camera had more noise that M Tapes did, so it was apparent to me that there may be some sample variation in these cameras. The A7rII is cleaner at higher iso's and holds more detail than either my D800e or D810 past 2500 iso.
Some people don't seem to have the issue with stuck pixels, others due not sure if this is due to their environment, like Eric mentioned. I live in a hot humid part of the US and was testing the Sony in pretty warm conditions.
Paul C