Do Qiagen RNeasy spin columns expire? - (Aug/16/2012 )

This might be more appropriate for the Qiagen tech support, but I wanted to get an unbiased answer. We have some old RNA isolation kits in the lab, and I'm wondering if I can use the spin columns from the kits. I'm also curious about the Qiashredder columns. As far as I understand it, the RNeasy spin columns are composed of something like 'glass microfiber membrane,' and I don't know why that would expire, but I've heard some people say they do, and others say they don't.

I don't think they do, the kits expire themselves as the buffers can change pH and some of the compounds may not be all that stable, but I don't think the columns go off.