I have spare parts for my AR's and Scar 16 like firing pins, springs etc....
I was wondering if there is a need to have the same for my Benelli

No. Just ammo. I had an old M1 Super 90 that I abused the crap out of. I probably put 10K thru it. Never needed anything. I now have a Benelli M2 Tactical that I am putting thru its paces. Benelli makes a very solid semi auto shotgun.

Carrier dog springs wear out on any shotgun with true high volume shooting. 10k plus rounds.

They do a lot of work.

Inertia springs could stand to be replaced as well after a while. Though most people don't shoot enough get to a while. (yes I know there isn't one in the M4)

I'm on my third carrier latch on my match M2, but that's due to modifying them to load so easy.

I don't own a single spare part outside of the stocks. How many shells do I need to toss down range before I should be concerned? I was kinda hoping to just shoot the shit out of this thing...

You can pretty much just shoot the shit out of it and call it a day (goes for any of the benellis). Maybe lifter springs if you change out the carrier (just a sooner replacement). I have a welded lifter on my m1 sbs and a taran on my m2 field. Neither have needed new springs yet, and the m2 gets used a lot for sporting clays and dove.

Most guns appreciate care more than unused parts in the drawer. There can be certain types that one needs a few parts for replacement. If something breaks, Numrich, Midway, Midwest Gunworks, & others are usually only days away.

Seems to me, field stripping, lube, & cleaning are the biggies to keeping things going. I have seen a fair amount of guns lacking proper care.

Unless you're a high op-tempo, sponsored shotgun shooter, I wouldn't be overly concerned about keeping spares on hand for an M4.

Clean it, lube it, shoot it, then repeat.

Great shotgun by the way. I love mine.