We recommend that a plan not be too long (30-days is a good number) for ease of management. You can create several plans of equal length and just take turns using them. This way, you don't have to spend the tedious time selecting food for a lengthy plan that is also inflexible.
To reduce a plan's length, simply click on the "Edit Plan" button and reduce the plan length; the program will cut out the excessive days from the last day of your new plan length.