The yarn sat in its tea bath overnight Sunday and most of Monday to maximise the dye effect. Then it was rinsed off in cold water and hung up to dry. Drying took another day, and the end result on Tuesday was this:
There's some colour variation across the skein, which is what I wanted, and it's a pleasant tan colour. Not sure how colour-fast the tea is, but there's no way it would go through a washing machine so I think it's safe. It still has the mohair shine to it and I'm pleased at how well it's stood up to the extra abuse. The skein ties were originally pastel green and those dyed up well too. Compare this with the skein's original colour!
It took at three or four rinses for the water to run clear and surprisingly, the end product doesn't smell of tea. This is definitely an experiment to try again. Next time I'll use an alum mordant before dying, recipes online seem to be 10% alum, 5% of either tartaric acid or cream of tartar, both by weight of the yarn to be dyed. I have a skein of white Cormo handspun just sitting in the spinning box...
(This project has been posted in the Knitting section for future reference.)