How long do shocks/struts last?

That oil consumption is not too awful bad in a car this old. It is telling you you are approaching end of life, though.

4 struts for this car, and the other bits that might be found needing replacement at the same time, springs , bumpers, steer bearings and mounts means you should consider replacing the entire assemblies. This makes labor much cheaper. RockAuto shows these to only cost $70-$130 each for the entire strut/mount and spring assembly with good quality struts (like KYB’s). 4 would be $520 for parts. With labor and an alignment you could get out the door for less than $1000.

Given the oil consumption, you may just want to start planning for your next car.

The oil use is on the high side, but on a Corolla with 270K on the clock I’d just keep an eye on it and be sure it doesn’t run low. It’ll probably go another 100,000 miles like this. It isn’t using oil that kills an engine, it’s running the level below the pump’s pickup tube that kills and engine. Granted, burning oil causes carbon buildup in the cat converter and the cylinders, and it is a sign that the engine is tired (you may not get up hills as fast as you used to) but the engine will run a long time in that condition.

I recall the days before emissions concerns when there were cars driving around everywhere burning oil. The never won any stoplight drag races, but they got the owners from point A to point B reliably.