Is there a maximum number of Tweets that Twilert will return?

For each individual Twilert search, 1,000-1,500 Tweets will be returned, depending on how many spam tweets Twitter manages to remove when it returns the results. This number is not limited by the number of searches you have setup and is not capped by account. Each time an individual Twilert searches for keywords (whether this is in realtime, hourly or daily) it will look to return 1,000-1,500 results per individual search.