Most brake drums do last the life of the vehicle depending on how much stop and go driving you do and how often you use the brakes.
Some vehicles may need the brake drums replaced sooner than others because some vehicle owners allow the brake shoes to wear down to metal and then it scrapes inside the brake drum causing grooves in the brake drums.
If you replace your brake shoes every 15,000 to 30,000 miles or at least before the brake shoes wear down completely then the brake drums should last 150,000 miles to as much as 200,000 miles.
Eventually brake drums do wear thinner and need replaced even if you keep the brake shoes replaced often enough.
I've had to replace my brake drums on my truck after 160,000 miles of driving.
You can have brake drums turned and machined but it's usually just as cheaper or even cheaper to put new brake drums on the vehicle.
I buy brake drums and brake parts on ebay cheaper than I can buy them in auto parts stores locally.