Josh
Welcome to the forum, you might want to have a look at the following FAQ which explain where everything is
Welcome to Benefits and Work ESA is an indefinite award with regular reassessment, the longest period for the SG is usually three years, but the only way to know with any certainty when you will be reassessed is for you to contact the DWP office dealing with your claim, your computer record includes the likely date of your reassessment.
Gordon