There are several factors the Loyalty Team take into consideration, but we don't specify, as we want people to play just what they're comfortable with and to enjoy the games for their own sake too. You do need to be on our email mailing list. This is worth signing up to overall, as there's plenty of other chances to be selected for an offer throughout the year. You can do this by going to My Account > Manage Details > Contact Preferences.
If you receive a reward, This will stay on your account for 7 days. However, if you do not claim this within a week, it will expire.