The bigger issue is that the meteorologists have a pretty good picture on where the ash cloud is, they also say which areas have the higher dust densities and which areas have low density of contamination. The issue is that there is little information on how planes react... There were two data points: Going through visible cloud is bad (causes flame out of the engines); flying in the background ash concentration causes normal wear. Only recently the Finish air force provided a third data point: flying through moderate ashes may require extra maintenance to the engine.
I am all in favour of getting more information on actual ash concentrations and the actual wear and contamination it causes to a plane flying through it. We should get to numbers like "flying for 10 hours through concentration x of volcanic ashes requires an engine inspection".