Switch the heater on at the first job, then switch it off at the last job. If you keep switching on and off, it does burn the burner out quicker, and you use more diesel. If your stopping for lunch or something, then obviously switch it off. I go through 2 batteries every 6 - 8 months, but it's not a big deal. Great bit of kit, we'll worth the money. If you have already got a system, speak to a local webasto dealer/boat yard to add one, you will find you may get it cheaper. I remember a while back while searching google, there was a guy, not sure where he was from, but a fully trained webasto engineer working from his van, supplying and installing night heaters ect.