It is hard to say. In theory, you can go for a long time as long as the oil consumption doesn't get any worse. I see a lot of vehicles that only see short trips around town. That is a killer on an engine. My advice is to change the oil religiously. Use a good quality oil like Castrol. Think about moving to a thicker oil. You're probably using 5w-30. Move to a 10W-30. I would also put that Lucas oil additive in it as well. Then just keep an eye on your oil level every 500 miles or so and top off as necessary. Going through a quart of oil every 1000 miles is not normal on such a modern engine, but it is not terrible. My 73 BMW goes through that much if not more. And the motor was just rebuilt. But that is normal for something so old. As long as your car doesn't get any worse, the motor could last you for tens of thousands of miles if you keep up with the maintenance. But if the consumption increases, the motor is well on its way to the salvage yard. Trade the thing in before its too late.