WFI Quality - Stability

I am working in a stability project for WFI. Our objective is to put some WFI batches in stability for 60 months. The WFI should meet European pharmacopea specifications.
But some argues that Eu.Ph. specifications are not enouth in this case, because there will be contaminations from the Tank, filters…etc which will not be detected with Eur.Ph. analysis. Should we develop specific methods to detect these materials? is the residue on ignition analysis usefull in this case (although it is not specific)?
Thank you for your help