My bought new 1994 Ruger MKII Target 5 1/2" is easily my high mileage champ. I used to keep count of all the bricks I had fired and eventually reached 30,000 rounds. At that point , some years ago , I stopped keeping count.
No parts were ever replaced due to failure. Although shortly after purchase I sent the gun off to Clark Custom Guns for a trigger job.
I really cannot be accurate on the number or malfunctions or jams through the years but they are very rare.