Thinking of the situation where fine-grained VA gets into the cooling channels inside turbine blades and / or forms a glassy coating on blades or stator vanes, therefore blocking leading-edge or other cooling holes, what's actually going to remove it? Therefore, further ash encounters must result in accumulation in the same area(s). If not, why not?
I think you are dead right. It wouldn't suprise me at all if there are incidents of blade shrouds departing the back end or vane trailing edges disappearing due to a very slow deposition rate of ash deposits inside the components.