How often do car wash as commuters with used cars?

Greetings! I drive an A-Class (W169, A180 CDI, EZ: 2007) with more than 150,000 km on the speedometer. At the same time I am commuter with 3,000 to 5,000 km a month, an estimated 80% of it on the highway. Up to at least 200,000 I want to drive the good thing, at least 250,000 separate me (if it comes to that). At the moment I drive once a week into the washing machine, because I value cleanliness – even if the car is relatively old and I am only the third owner: I love my A-Class Mr. Wa sh (there it goes weekly) now offers a flat rate, with which I can have the car washed inside and outside for 100 € for three months as often as I want. Since I would save 20 € for the weekly outdoor laundry and receive an interior cleaning almost free of charge, I would like to make use of the offer.My question: Can I overdo it as a commuter with such average mileage and especially in this weather with the laundry? Would three to four times a week at any time in a way harmful to the car? In other articles I was written here about new cars or newer cars.. I got my own with individual scratches and dents as well as the above km on the tacho (about three months ago), which is why I can’t personally see any disadvantage in it (the micro scrapers I will probably be able to handle). Do I overlook something? Should I leave it with flatrate at once a week?