My girlfriend has a small PR2 blog that is very general and she wants to start getting serious about making an AdSense income from it.

She is doing some keyword research, finding long tails where she can rank in the first few pages but we're noticing that the AdSense ads don't update very often, maybe once a week meaning that the front page always shows irrelevant ads for the top (latest) entry.

My question is in two parts, is there any way of getting AdSense to crawl the blog more often, or should she configure the blog to only show one entry on the front page?