That depends on a lot of factors, including size of the stock, temperature that it was brought up to, ambient air temperature, whether it is in contact with a heat sink or not (the anvil) and for how long, etc, etc. Im sure even humidity has an effect. Its very hard to place a specific number on that, but you can usually figure on a few minutes before it loses all glowing heat.
Yup. Thats all hammer control. Make sure your anvil is at the proper height for YOU so that your hitting the steel with the flat of the hammer, and its not pitched towards the front of the hammer or the rear. Many other smiths may consider my anvil too high for their personal tastes, but its right where its comfortable (and effective) for me.
Take your time with your hammer blows. Well placed, accurate, firm hits, are much more efficient and effective than trying to smite the steel with all of your force. Using an appropriately weighted hammer is a must. Try to place your blows so they overlap each other (the middle of your hammer strikes the edge of your last hit.)