We also clean mattresses in your bedroom. These are used the most and tend to collect dust and body oils and sweat. It is recommended that you thoroughly clean your mattresses at least two to three times a year. Though vacuuming and using dust covers can protect your mattresses, you will still need to get them steam cleaned. You can try and steam clean the mattresses yourself but it is a chore and you may not be able to get them to dry well enough. This may cause mold and mildew to form on your mattresses.