It really depends on several different factors, but I can tell you what I do to keep my carpet clean. I have three dogs that malt so for me, hoovering is a daily activity. I also like to keep the carpets smelling fresh so about once or twice a week, I will use a fragranced product and leave it on for a few hours before hoovering it. This type of thing is inexpensive and can be purchased at most supermarkets.
However, when it comes to giving the carpets a thorough clean, I do this about once a month. I pay Abracadabra Cleaning a company that offers carpet cleaning in Chippenham, Wiltshire. They usually come once a month and do a proper clean on all the carpets. This removes any dirt that the hoover can’t get to and gets rid of dog hairs that have may their deeper into the pile.