Indeed this is true, the pre-motor filter is located down the side on the DC07. It should be washed every 6 months under cold water, and then left to dry for 24 hours or until it's COMPLETELY bone dry.

The post motor filter should never be washed, I would replace it every few years, though the HEPA ones I believe are designed to last 10 years I think.

Hope this helps! :)

Tim.