I have had many sites come to me and want to do a "test" campaign for a week. You are just wasting money if you try this. Campaigns are meant to run for long periods of time if you want to see results. Build community trust while you are running your campaign and run other promotions as well to get players interested in trying your casino out.
Yeah I suppose you are correct too, before starting up something like a signature campaign I believe the casino should have the understanding that nothing actually ever explodes overnight or if possible like the way you said is one way @managers enlightened them. Some casino might take it as an easy way to advertise since the forum has high traffic in terms of active gamblers but many people actually need to be confident about the casino before throwing up $money to the casino and it takes time and moreover multiple advertising strategy is always better but that too still depends on the marketing budget of the casino.