Depending on the reason for banishment, it can last from several RL days to several RL months. Dying will not have any effect on your banished status; what may happen is that if you die while banished, you will not be allowed to reenter Arda.
You can see whether you are banished still by checking your info. In some cases you may find out for how long you are banished by asking an important person in the area you are banished from.
Generated on Sun Jul 5 23:36:17 2020