Is my car still in good conditions?

I just bought a 1992 Honda accord last year in March and it was in great conditions. I've taken good care of it and have done the oil changes it needs. For the past 4 months it shakes crazy, but just from the steering wheel, and i got that checked out but the mechanic said it's no biggie. My question is, since its old, can i drive about 70 miles a day, my job is about 35 miles away so i want to know if it's in ok conditions to drive that many miles a day.

You didn't mention how many miles were on the car. This would make a difference. If it is not consuming much oil between changes, then the engine is probably in good shape, and as long as you do not have any transmission or driveline issues, this daily drive should be fine. The shaking is most likely due to tires. If your tires are worn, replacing them with new tires will probably cure this. If you do, make sure the tire shop balances your wheels.

If the car shakes just when the brakes are applied, the front brake rotors are warped. That's annoying and interferes with stopping safely. It isn't so hard to fix. If it shakes all the time, more when you speed up, have the alignment checked and have the wheels and tires checked for irregularities. That could be it, or the car has started falling apart and needs more complex repair. Remember, it is an old car.

First know one knows if the car will last each car is different. Second your mechanic should have told you what the issue was. All people here are going to do is throw out wild guesses. You have to look at the entire system first check the tires if they arent balanced properly then you will feel a vibration the thing is it gets faster as the car goes faster. If you only feel the vibration under braking then warped rotors. If it is actually shaking and the steering wheel is actually pulling from side to side then you may want to look into your tie rods you can check this by looking at the front tires and look at the inside tread it will be more worn than the outer part.