That's cause is an initial deposit bonus, not a second.
Beyond initial deposit bonuses you only get anything from deposits if its on a special bonus offer typically received from the site via email. 888
typically has a reason to deposit almost every week, although some weeks to get full value you would need to deposit a few hundo .... the most common one I see is when the weekend is approaching you make a deposit and get free 7$ tickets for mtt's or get 50% mtt buyins back up to a certain amount .... I think both of the bonuses as awesome (I just hate getting struck with the conversion fees when depositing there so only take up a deposit bonus now and then)