Not very often! You should vacuum the rug once a week using suction only, unless your pet or a child has brought inside surface dirt which has dried and needs the revolving brush to shift it. Powerful brush motion strips your rug and is not necessary as they are remarkably resilient to dirt because the wool is still naturally quite oily . These oils, lanolin, act like a natural protective treatment.
Rugs are NOT self cleaning but a heavily patterned handmade Persian rug will hide a multitude of sins! We recommend having your rugs washed or if silk or cotton, dry cleaned, once every five years. Please ask a rug specialist to do this for you as very often your local carpet cleaner will be clueless as to what they are dealing with. If you MUST do it yourself then vacuum it intensely , front and back, until no more loose dirt is in the pile, and scrub using pure soap flakes in cold water. Depending on the provenance of rug you may still experience colour bleeding, especially with a chrome red into cream. Consider this a warning!
DO NOT USE A RENTED ‘ALL PURPOSE’ MACHINE AS THE SOLUTION SUPPLIED WITH THEM IS TOO HARSH FOR RUGS OF ANY QUALITY.
Once finished brush the pile back down so it lies flat in the correct direction. Allow to dry naturally in sunshine, preferably on concrete or tarmac and raise up to allow air to circulate. If small enough hang it up to air dry in the wind.
However if you have spilled red wine, tea, coffee or children’ drinks (especially that very purple one ! ) call an expert immediately. This also goes for any kind of urine staining.