How long should I let my tea cool before adding unpasteurized honey to it?
Well, after a cursory look online, it looks like the honey shouldn't be heated above 95 degrees Fahrenheit, or what a "natural temperature" of a bee hive would be. Assuming you're drinking black tea, you are boiling the water, so it starts off at around 212 degrees Fahrenheit (near sea level). How long it will take for the tea to cool will depend on what the tea is in and how cool the room you are in is. So, in other words, there really isn't a rule of thumb for the cooling part since the environment the tea is in will dramatically affect how long it takes to cool.

I'd just use a thermometer and check it the first couple of times you make the tea.