I did have better success with 85 than I saw with 128... but in hindsight I think my experience is not very useful.
I had bought pixels in 2 batches... each batch had 20+ strings of 128. Inspecting them, they both looked waterproofed to the same degree and I thought they were all IP68 (new gen). Turns out that one batch was IP67 and the other batch was IP68. I found that IP67 is flat along the cylinder that holds the board/chip within the pixel. IP68 is fully-rounded. So my testing was done with an unknown combination of pixels. I did repairs because of malfunctioning pixels -- and when I did this I mixed in IP67 with IP68 strings, and vice-versa.
The other thing that I did that causes me to suspect my findings... I had my strings still in loops when I tried to burn them in (in my dry garage). After 6-7 hours they started acting flakey. When I cut them down to 85 nodes, they no longer acted flaky. I now suspect heat buildup from having 10 strings each in their own loops sitting on my shelf.
So, I have no proof that using 128 IP68 pixels, stretched out into a string will not give great results. Others have not had a problem.