A fence is usually in place because a unit is going to deploy or in just returned from deployment or an individual is on a special assignment. You should be able to go over to your local S-1 shop and ask them to pull up your fence date. This date will show the last month the fence is effective. If you have just returned from deployment you can usually ask that your fence be lifted with no problems. Otherwise it is difficult to have a fence lifted.
Does being in a fenced unit affect my request for retirement?