He used to drop into my chambers once in a while to smoke, and was first-rate company. When I gave a dinner there was generally a cover laid for him. I liked the man for his own sake, and even had he promised to turn out a celebrity it would have had no weight with me.
The owners manual on every vehicle should state how often the manufacturer recommends that you tune up cars, but as a general rule it is every two years or 30,000 miles, whichever comes first. Driving under extreme temperature and weather conditions will make parts wear out faster, however.
How often can you train with a low intensity/high rep approach? A toning style core routine can be performed 4-6 days per week once you have built up your tolerance for those exercises, but if you become overly sore you may need to take a 48 hour break to allow muscles to properly heal. Just make sure you take at least one day off each week, even if you never get sore.