Most longtime firearm carriers will recommend a cleaning of the firearm and magazine once a month, ideally after a visit to the range to practice with it.
Carrying can cause damage from bumping into walls, furniture, car doors, etc. Carrying also exposes the firearm to all sorts of dirt and grime such as lint from clothing, dust and dirt from hands and the air, small particles wearing off your holster and, as you pointed out, spills.
You should also fire your current carry ammo during one of your range visits and replace with fresh ammo. How often depends on whether you can afford more SD ammo, and whether or not you can find it in stock. Once every three months might be a decent rotation schedule to make sure that ammo isn't absorbing moisture or building up corrosion from rain, a sweaty body, humidity, and so on.
i've seen some carriers say they clean their carry gun at the end of each day, because they might choose a different firearm to carry next and don't want to leave an uncleaned/un-oiled pistol sitting in the safe for an indefinite period.