Running the vehicle ever so often is definitely better than having it just sit. It has to be done right, however. You have to reach proper operating temperature in order to minimize condensation build up. I would run it at least one hour each time. Not just 15-20 minutes. Short runs are worse than doing nothing.
Do this at least every two months, maybe more often, like monthly. Change the engine oil once a year. Use fuel stabilizer in the tank and keep the tank as full as possible. Change the brake fluid every two years. If you want to store it for 6 years without running it you must go through quite an effort to prep the car and the opinions what needs to be done vary widely.
