During the very brief time I pioneered, this was a huge problem for me and I tried without success to get a straight answer on it. We were a very rural congregation and DH and I lived an hour away, over dirt roads, from the hall.
Many times I would pick up another sister who lived even farther, to go in service. So I would spend an hour and a half or more *in the car on the way to the service meeting*, and then the same on the way home! It became obvious to me that counting time "from the first door to the last" did not REMOTELY express the time and effort it was taking me. In fact, I don't think it would have been physically possible for me to get 90 hours a month in that manner! The advice the elders gave? "start your time before you leave home"...SERIOUSLY? How am I supposed to do that? Make a phone call to someone at 6:30-7:00 in the morning? Stop at the farm down the road on my way out and back so I can 'count the whole time'?
It just seemed totally silly that I could 'count the time' by following such a 'strain the gnat' kind of method...and not if I didn't. And of course this was one of those subjects (because of the geographic situation of our hall) that you couldn't really ask people's opinion about or 'what do you do' because following 'the letter of the law' was so obviously unrealistic but no one wanted to be caught saying that, or admitting what they actually DID, in case they got told they couldn't do it any more.
This subject was one of the wierdest aspects of being an active JW...considering how every other part of our lives was micromanaged by Society directives, they sure were vague on this one...for obvious reasons!