Tea & a Thermos

Semi-silly, but will the taste go bad after a while in a thermos?

Not silly at all.

If the thermos inner walls are metal, then my experience is that the tea would taste 'off' almost immediately. The acids in tea just do not get along with metal, IMHO. Too reactive.

To me, tea tends to taste 'wrong' (or worse) when drunk (?) from anything other than porcelain/china or glass.

And let's not even mention styrofoam.

Thanks, that was my concern.

The one thing that I learned about hot tea in a thermos is that you need to make sure the coffee is completely cleaned out of it. Otherwise, you're gonna have odd tasting coffee instead of tea.