The way I was taught was 155-165 degrees for 30 minutes. And my extract batches never have had an astringent taste.
Also I found out by experimenting through several batches that my 12 cup coffee maker (used exclusively for hot water) heats my water to 165 degrees. So during the steep I make another pot of water and sparge my grain bag through a colander.
That's 1.5 gallons if anyone's counting