Let's look at your 30 pics & a banner every 5 pics set up - with that, you'd have 7 banners (if you went by the banner, 5 pics, banner, 5 pics....5 pics, banner thinking)
By taking that over 3 pages & using the same banner, 5 pics, banner.... thinking, you'd get 9 banners up there for them to look at
Last time I looked, 9 ads was more than 7 ads
