How long does it take for image ads appear or disappear?

Once they are switched on or disabled

[Scurramunga]

I apologise if this question has already been asked, however I switched this function off a few hours ago and I sitll see image ads on my site. If anybody knows, I would also be interested in knowing how long it takes for images ads to re appear once they are switched back on again.

[Scurramunga]

Just another question.

Google says that that your default text or image ad settings in the control panel can be overridden on an ad block by ad block basis by choice of code that is contained within each block. eg. I opt for text only on the image panel but I decide to have image & text on a certain page by choosing the relevant code.

Is the reverse also true? that is if I had orignally placed a block containing the option for text & image code: google_ad_type = "text_image"; Will I be able to opt for text only by changing the settings on the control panel or do I need to go back and remodify my blocks so that they contain now contain the code :google_ad_type = "text";

Thanks