How often should you spiritually cleanse your house when you come in contact with a person that seems to have a lot of negative energy around them and does not do zero cleansing as in burning sage/palo santo or take spiritual baths. Is it considered too much when you sage the place immediately after they leave your house if you see them usually once or twice a week?
How often you spiritually cleanse your space depends on your preference for doing so.
You may wish to consider how much time you are willing to spend cleansing, you also need not cleanse weekly after contact with this individual if you would rather not. Once a month is reasonable if you are in contact often with someone you may not resonate with.
Think of it this way.. How often is one supposed to clean their house mundanely? Daily? ... weekly? ...once the dust-bunnies gather and threaten to revolt?
In the end it is up to you and how often you feel you need to. If you are feeling a general heaviness to the air that lingers for longer than you would like, do a cleanse.
But bear in mind the golden means as well. Relying on cleansing can become a sort of addiction and paranoia, just like with mundane cleaning. Unless experiencing an unusually potent negativity for a prolonged time, or having your space invaded by a deliberate malicious entity, the energies of your space should be able to maintain themselves.
An alternative suggestion would be to lay out a more permanent form of protection/cleansing. Think of it as installing the spiritual version of an air filter.
The easiest method is to hunt down any form of a quartz cluster. Clear quartz, smoky quartz, and amethyst are super common and relatively inexpensive. It doesn't even need to be very big. Clusters that are just large enough to sit on your palm are fairly easy to get. Place the cluster on a windowsill, ideally where it can get hit by direct sunlight (it charges and clears the crystals) and on a small mirror coaster for a magnified effect.
Failing that, place the cluster on the living-room coffee table, or otherwise in whatever room you spend most of your time.
Other stone options; blue kyanite, Apache tears, obsidian (or snowflake obsidian), tourmelinated quartz, citrine, malachite, or labradorite.