man who is naked under his kilt gives vocabulary lesson

[vorpallemur]

It looks like the time scale is thousands of years for the flow of glass.

http://www.jimloy.com/physics/glass.htm
That is extremely high viscosity, but still viscous. You're right about old windows not showing these sighns, though.

Time scale is a couple million years. Glass is a solid. Period. Anyone who claims it's a liquid is simply wrong.