I likely have the highest round count in the country through my Grizzly, I've stopped counting the rounds through the gun after 65K shots fired..........LEGIT.
500 to 1000 rounds fired in a weekend used to be this guns average day out.
I purchased my gun from Wanstalls back in 2008 when these guns first came into the country and it has been my go everywhere gun for almost 10 years now.
Been through every climate our nation has to offer including salt water exposure and just last week did I actually break a part on the gun, the firing pin of all things finally gave up.
So parts changed are a Remington firing pin now, No-Jam follower (factory one never failed me I just wanted the extra good feeling) and only replaced the magazine tube spring when I installed an S&J +1 Extension last week.
They are a heavy gun especially in regards to the barrel, may as well call it a bull barreled shotgun compared to a standard 870 Express barrel.
I've never touched my extractor as it has never given me a reason to bother with it.
My guns finish is well seasoned as I stripped all the bluing off of it years ago and ran it bare metal for a cool survivor gun look then krylon bombed it a few times now.
As for the guns condition the first 10 pictures on this link sum it up pretty well, and the last 3 pictures are how it sits right now.
http://imgur.com/a/1r6Zi
So given all of that abuse and only a $20 firing pin as broken after all that use.......I absolutely trust my life to this gun any day of the week.
My gun was not perfect and had a few rough spots in the action when I got it but its smoothed out enough over the years I just don't even notice it anymore.