Many folks have said that.
I've never know anybody with any Toyota where the engine died before 150k. Most of the people I know who have owned their Toyotas long term have between 200k and 300k with no engine problems. I have no doubt that Toyota has engineered the engine in the current generation Corolla to be just as reliable as the previous engines. As long as you maintain it properly, the engine will outlast your interest with the car.
My interest with the car pretty much ended the minute I drove it off the lot. It is strickly a how-cheap-can-I-make-my-100-mile-commute decision. It's been good so far, but the longer it lasts the better that equation gets.
So, I'm already out of love with it. Even when I do decide to get an around-town vehicle (boy, do I miss my F150) when the 'Rolla reaches beater status (at 55k on an '04 model, she's still a loooong way from beater but it won't take long to get there), I'm hoping to drive it into the ground and leave it in a flaming heap on the side of the interstate.
Then, I'll probably go pick up another cheapest-to-drive car. If the 'rolla makes it to 300k, it'll probably be another Corolla. Something less than 200k, then there are more attractive alternatives.
I would suggest you sell your car right now and get yourself one that gets 60 MPG. You are already dissapointed with the car and although the fuel mileage is good, there are cars that get much better. If you don't like the looks or the appearance, the reliability and dependability won't matter as much. You will not be happy with it unless your attitude about it changes, thus my suggestion for you to change it now. Find the very cheapest car to drive and then get that one. You may be equally unhappy, but you will not be spending a lot of money for that same unhappiness, and that may give you some satisfaction. Why drive a car you don't like??
I think you want to know at what point will the cost of repair outweighs the cost of getting rid of it and getting a replacement. By common practice, there is at least a 75% mark-up on parts and that does not include any labor to change those parts. Take the price you pay for a new car from a dealer and multiply that by 3. That is what it would cost you to get the same car, buying it piece by piece. Double that amount and that is what the repairs would cost you in labor to have someone else change the parts for you and do the normal maintenance. Your car has always been depreciating from the time it was driven out of the first dealership.
I have had cars for 12 or 13 years and those were the old cars. New cars can go even longer before it would cost you more to fix than it would be to replace. Your interest in the car will be long-gone before then and you will get something else. Just sell the car now to someone who wants it for what it is, not for how long they can stretch out it's life.