... With a marketing campaign, you create a lot of interest and have new players that will sign up, but you will not just hold these players active just by doing giveaways and events. That's the most difficult thing, keep your players motivated; you can only do that with adding new features to the site, adding new games/slots, ...
It's good to have an ongoing marketing campaign, it's part of branding all the big brands in any industry always have marketing everywhere because they want continuous people awareness, McDonald, Coke already number one in their respective fields but they have a new campaign almost every month, they always want to get into the mind of consumers, this also applies to gambling here you want gamblers to think your gambling site when they have the urge to play.