The majority of cookies expire in 30 days, but you can also choose to clear them manually whenever you wish through your internet browser settings. Google Analytics cookies may remain for longer, but can still be cleared out whenever you wish.
As an example of how cookies are used is on the number checker page. Once you have checked a line of numbers and leave the website, you may notice the numbers are pre-selected when you return, in order to make it as easy as possible to check your ticket again.
You can delete your cookies at any time through your browser history settings, and it is completely up to you when you do so. You can also disable cookies completely in the same settings area, although this may make interactions with this website and others less user friendly.