I'm just wondering if the aircraft pitot/static systems will be affected if flying through ash cloud for months
Volcanic ash is made of very fine particles (down to 1 micron) that can even penetrate easily the most tightly sealed parts. A total blockage is a very extreme situation likely to happen while flying in the "ash" for hours ... nevertheless a relatively low quantity of volcanic ash may be sufficient to disrupt the flow of air in the probes, thus generating unreliable speed indications.
Suggest reading the following Airbus notes on Volcanic Ash Awareness:
http://www.airbus.com/fileadmin/medi..._ENV-SEQ06.pdf
Safe Landings,
fredgrav