The rental market moves so quickly now that you can’t really look more than about 30 days out. Typically landlords/property managers will only hold the property for a week or two once an application has been approved and a lease signed (or shortly after it’s listed as available date).
Properties come and go quickly that if you find a great property more than a few weeks before you are planning to move it may not necessarily be available when you’re ready. It is a great idea to start researching the areas where you might like to live. That way when it’s closer to the time to look, you know what areas, neighborhoods, towns/cities you are interested in and can narrow down your search.