Posted before but we used to do a job at 80' where we did a stairwell outside one day, inside the following day.
After the first clean, they were absolutely spotless every time.
Cleaned 3 times a year.
You can't really guarantee a perfect finish every time with WFP at any height.
You only need one gust of dirty wind and the crap will stick to the water droplets.
But yeah, the planning is the hardest bit.
The job at 100' was a 4 day job that started end of January and wasn't finished until nearly a month later!
At 80' (IMO) you need single figure wind speed with no gusts.
In England, that ain't always easy.