How long after the extinction of humans will the evidence of their existence disappear from Earth?

I'm gonna claim that manmade glass objects will last tens of millions of years in the driest environments.

I looked it up, ancient Egyptian glass bottles started around 1500BC, so 3500 years ago.


This obsidian (volcanic glass) hand axe is 1.2 million years old. Not suffering much from weathering or other aging. Obsidian will weather in the presence of water, but it takes a few million years. I'm gonna assume some manmade glasses have similar lifetimes.