For me it seems utterly useless to clear the last X weeks of browsing data and keep everything before. I'd love a feature in exactly the same place (clear browsing data from this period) where I can delete everything up to last week. That is, keep all of this week and delete all that was before last week.
The reason: I use Iron on a portable USB stick and the profile folder seems to steadily grow and grow. But if want to keep the most common URLs and the new tab overview screen, I cannot delete the entire history.
How difficult would it be to include this in the next build?