I've tossed out lots of these with no precautions. Unfortunately before I realized how deadly they can be. Just because the mesoliothema can be 30 years away, don't ignore it. Get a pro's advice on encapsulation.

See link.

Here is a link that might be useful: EPA: Asbestos in Your Home

If you can, post a pic. I don't know why a cold air return would be insulated with asbestos.

I'm not an expert on this, but if the asbestos is completely enclosed in drywall, I don't see what the danger is.

The danger is the possibility of the fibers getting into the air ducts. If the material is not labeled with a sticker you will need to have a sample tested. While you're at it have any old resilient floor tile or pipe insulation tested.