I have 210,000 miles on my vehicle. Gets the same mileage as on mile 1 and burns no oil and has same amount of power. How mamy more miles can I expect? I would like to go to 300,000.
No one can say. Just keep doing what you’ve been doing.
Speaking for myself and some of my relatives and in-laws, we have gotten 400k+ on a number of vehicles and they were still running well.
Eventually boredom sets in. 
today it is usually something else that causes a vehicle to be discarded, the engines just keep on going, modern engines and better oils, gas etc. the otehr problems, transmissions, struts, suspension etc give out before the engines
Your engine will last to the 300K miles mark but that is many years away. In between now and then your A/C will take a major hit about the same time your transmission dies, and you need a new set of tires anyway. Tough call; you’ll cross that bridge when you come to it.
I got 325K miles on my truck before my wife got into a fight with a retaining wall. The wall won, as always. I was going for 1/2 million, and felt I could reach it. Still, I sold the engine for $800. Still miss that truck. 
What kind of car? What type of maintenance do you do? What type of driving do you do? Details? I currently have an '89 accord with 430,000 miles on it, I’m going for half a million.
Yeah, it’s called Jiffy Lube. 
Like with all things, the engine will last until you wreck the car, you lose a bunch of oil all at once, or you get tired of the car itself. Just depends on how much money you’re willing to spend.
How big is your wallet and how is your luck
At 210k miles I would be gracious for every day the vehicle start and runs without issue at this point. Remember 150k-200k is the period most modern vehicle have without major issue. Your past the point now so don’t expect miracles.
What I mean above is that NEW through 150-200k is the typical period of ownership across all cars without major issue.
Many vehicles go over 300K on their original engine. Keep following the maintenance schedule and watch the miles rack up.
I have 117K on my 98 explorer. I want to keep it a long time. All is well. Very few items have gone wrong. I am trying to find the answer to this: After 120K miles do you start using the service manual from zero miles and fix/do maintenance all over again at the recommanded mileage? My manual runs out at 120K. Are there service manuals made for over 120K miles? Thanks for any ideas. Bruce
300k is plausible however it has to be over a reasonable period of years. Engines seem to have a life of about 12 years/200k miles before major repair.
No one knows but 400,000 is not unrealistic.
LOL. mine is currently 380K miles at 25 years and counting.
All engines are NOT created equal…A 20-22R Toyota or a 318 Chrysler will run FOREVER but a Subaru, maybe not…