I’ve been using this DH with my car for about three months and haven"t noticed significant vampire drain. The presence sensor functionality in the device handler is based on the Poll() method, which SmartThings calls periodically. The timing of this is a little variable, so it can take a while for arrival/departure to register.
It depends what your use case is as to whether this is a problem. If you want something to happen immediately when your car arrives/departs, then this is not really a suitable solution (and probably never will be as increasing the poll frequency obviously increases the frequency of contacts with the car)
Hope that helps!