Hm, I see your point. I may be confusing the way general users use their browser with how I use mine. For example, I'm currently at over 9 days of uptime on my laptop. I could very well go days without restarting Firefox.
Also, one of the issues I've heard on these boards is people want the art to change more often.
I also imagine that people do look forward to seeing add-art and check to see what's new when it's updated. But there's no way for me to know that. Hm.
Still, the dialogue comes up only every two weeks.
You might be right. This is fairly subjective, perhaps it could be solved with a poll of users. I will ask the other developers what they think as well.
We would have to consider this change for the next release. I have added it as a ticket
http://dev.eyebeam.org/projects/add-art/ticket/139