I have 8 Ender 3's, all pretty close in age, I have upgraded several with Aluminum Bowden Extruders. Those I have not, are starting to have issues with extrusion as seen in the pictures. Save yourself some frustration and swap it out early.
Here is my guide:https://makersteve.com/2019/03/19/a-tale-of-eight-enders-aluminum-extruder-upgrade/
You should print this filament roller guide. Works Like a charm.
Yes folks! It's the poorly designed spool holders which cause this. Take it off the top of the printer, how stupid. Move your spool down next to the extruder so it's going in at a more level angle, thereby reducing the friction causing the erosion. I just rigged a dowel rod and some 608zz bearings, and other stuff from around the shop for support. Even if your not Maker Steve :) and only print a few times week, your prints are likly to come out better. Or at the very least, put off the expence and work of the upgarde.
I replaced the arm with a printed one that had a slot for ptfe tube. No issues with damage.
You can also print out a filament guide. Wouldn't that extend the life of the stock part?
I did try a few, the trouble is they're not very strong when printed in PLA, they crack and snap quite easily. The best one I found was a simple hook but even the base on that snapped after some use. For £7.99 its hardly worth the hassle.
Fitted one today, £7.99 from ebay.
Ooh yeah, that's bad. I'm starting to get filament cutting into mine so I'll probably just print a new extruder arm and swap it out when I start seeing issues. A Bondtech BMG is near the top of my upgrade list though. Just short of replacing my twisted Y axis extrusion haha.