Thrusty;

I assume that you drive from place to place then walk for a few minutes at a time to deliver then jump back in the car/truck and drive a few more minutes and repeat. While the cumulative work is impressive the aerobic stimulus is probably very low due to the short duration of each effort and the intermittent nature of the efforts. Recall that the biggest stimuli to aerobic adaptation is the (continuous) duration of the work.

Of course it depends somewhat on your current level of fitness as to whether this will contribute to your base or not. For an unfit person (which I feel safe in presuming you are not since you are on our site) this would definitely help build basic fitness. However, the fitter you become the harder it is to become fitter.

This work certainly will not hurt your fitness unless the fatigue from it prevents you from doing more effective training. We see this climbing guides whose job requires them to be active often all day but for fit people like them does little to improve their fitness while making them too tired to training after work. This seems like what you’ve got going on.

Scott