There's no time limit on your purchase until you've actually started the game. That means you can buy it months in advance if you want to, and it will be ready and waiting for you when you're ready to go. Once the first person in your team enters the code & confirms the start of the game, you'll have 24 hours to complete it. So don't worry if your new puppy (or child) suddenly needs to take a rest stop in the bushes, or if the Ocado delivery turns up - you'll have plenty of time to finish your game even if you're interrupted.