So I found some nice bags of metallic 5" rounds in my local 'cheap' shop. They are Qualatex, but the old branding so I don't know how old the balloons are.

They only wanted a pound or so per bag so I grabbed them.

Are there any downsides of old balloons? I imagine the material my have weakened?

You will know if they are ok with the first one you blow up.
They start to feel thin and poppable the older they are.

Thanks Graham. They seem okay. Was just wondering more about the health and safety side of things? Can the chemicals in the materials become dangerous overtime?