Every other month since the car doesn't get that dirty.
I remove all the floor mats and vacuum the interior, sometimes I vacuum the trunk if it dirty. Then I just lay all the floor mats on the garage and vacuum them. The interior windows are cleaned then I wipe the plastic interior parts with a dust cloth. Sometimes I use protectant (303, Armor All) on the plastic stuff. On the floor mats or seats I just spot clean them if there is any visible stains. Probably should shampoo the interior since I have not done that since I had the car.
I remove all the floor mats and vacuum the interior, sometimes I vacuum the trunk if it dirty. Then I just lay all the floor mats on the garage and vacuum them. The interior windows are cleaned then I wipe the plastic interior parts with a dust cloth. Sometimes I use protectant (303, Armor All) on the plastic stuff. On the floor mats or seats I just spot clean them if there is any visible stains. Probably should shampoo the interior since I have not done that since I had the car.