I ended up erring on the side of caution with my first steep and took the (awesome!)infuser out of my travel mug altogether after about ten minutes. In a stroke of brilliance, instead of dumping the tea leaves I put the infuser in my work mug, that way I can resteep without any mess. So, that’s what I’ve done!
I know that I’ve drained a lot of the flavour already, but I figure I might as well maximise what I have here at work. I think a big mug of spearmint will come after this, since I’m really enjoying just filling the travel mug with tea you don’t have to worry about. It keeps it substantially warmer than my work mug as well, so I don’t have to get up and make a new tea every 20 minutes.