I got a 12 gauge 870 express for my 16th birthday and shot that gun for the next 25 years, I used it for everything that flies: ducks, geese, pheasants, snipe, doves, grouse, turkeys, etc. Don't know the number of days in the field, but well over a thousand birds. I hunted it in salt water marshes to 0 degree F freezeouts.
The ONLY mechanical issue I ever had was the wood finish wore off around year 15 and the wood foreend swelled and wouldn't slide on the magazine tube. At that age, the metal finish was wearing as well, so I sanded the whole thing down and painted it. That was actually a fun project, but I'm no artist. It looks better at 10 yards than 2 feet.
I would probably still be using it today, but when my son needed an upgrade from his 20 gauge single shot, I got a used Winchester SX4 for him. I liked it so much that I bought one for myself!
While I will always hold that gun with a bit of nostalgia, I understand that the quality of the 870 tanked in later years. I never used any Remington rifles.