I pour my tea with the water nicely steaming, but never boiling.  I have a feeling that the 45 second rule would be great if you want to reuse the tea leaves for a second cup of tea, but I prefer to leave my tea steeping for at least 5 minutes (sometimes 10 minutes).  After that, I remove it, because there isn't much of anything left.

If the water is boiling, it can draw out the bitterness, and "cooks" the leaves as if you were making boiled soup.  That's a good approach for roots, bark and stem teas, but leaves and flowers need less heat.  

Quoted from 6982

  
45 seconds?  I usually leave it in the cup, is that bad for the leaves?

Some of us supertasters really notice the increased bitterness of green tea after steeping more than a minute or two, depending on the variety of tea.  

Victoria, you are our TEA Ambassador~!!  

Quoted from 6982

Victoria, you are our TEA Ambassador~!!  

Thank you!    But actually Kristen is the expert.  I just do what I like.