On my 89 XR7, I change oil, reset VMM and it tells me it needs changing again within a mile. Then next time I start the car it may be OK. Seems like it has a mind of it's own. That's why I think the VMM is gonna get ditched in my car. I can simply watch the odometer and change oil when it hits 5000 miles (Mobil-1) like I have done with any other car.
So as far as accuracy, I would say, if all sensors and the VMM itself are all new then it would be accurate, but being as old as these things are I wouldn't count on it.
Heck, I can let the washer fluid go EMPTY and drain out the coolant overflow tank and they NEVER light up. Never seen anything as far as low fuel come on either.