The answer to this question is extremely subjective, however, here is some wisdom that I can offer:
#1) There is no such thing as "too much" when it comes to detailing your car. If you have the funds to do it, and you want to, then a weekly plan is not only great for always driving a clean car, but also keeping your car in showroom condition for its entire lifetime.
#2) You will not damage your car by detailing it as regularly as once a week. If anything the opposite is true. Regular cleaning, especially as often as weekly detailing, will extend the life of your cars interior and exterior by leaps and bounds. Regularly protecting your car's dashboard, fabric, leather, and paint from the damaging effects of the sun and elements, is a very, very good thing.
#3) Once again, maintenance is better than the cure. Customers sometimes get frustrated with me because of the price I give them in order for me to do a complete detail on their car. What they do not realize, is that if they would have had their vehicle maintained prior to calling me, that price would not look nearly as scary. The cost of detailing a car that has been left to sit in dirt and grime versus the price for a maintenance detail is just not even worth comparing. Save money, and drive a well-maintained car, it just makes sense.
#4) Obviously not everyone can afford to pay for a weekly maintenance detail plan, and that is completely understandable. In cases like these, there are other paths that may work. Once again, in order for it to be considered a maintenance detail, and fall under the pricing of a maintenance detail, it must be done within a maximum time span of 8 weeks. Of course, the weekly maintenance detail price will not be the same as the monthly or bi-monthly cost, but the monthly or bi-monthly plan may still be a much more viable option for your specific situation.