I used to change the o-rings every time until I managed to pinch the big o-ring on my GoldWing (similar setup to the CX but larger) when putting it together. Big puddle of oil under the engine and no option except putting the old one back in. After that I decided they didn't need new o-rings every time so I started changing them every other time. Since I started buying filters that don't always come with new ones I change them if they look like they need to be changed, which isn't often.
The last time I remember changing an o-ring was when I replaced the engine in the GoldWing (long story involving better gearing for the sidecar). I actually replaced the o-ring with the one that came in the Athena gasket kit and a couple of weeks later I noticed oil dripping from the engine, which turned out to be coming from the oil filter housing. When I opened it up I found that the o-ring, which had protruded from the groove normally when I installed it, was now too thin to seal.
The one I replaced it with is still sealing several oil changes later.
I think I probably replaced the one in the GL500 engine before I put it into Eccles too but I'd have to check my notes.
FWIW, one of the machines where I worked had a counter that was driven by a plastic belt with a round cross section, which broke eventually. Instead of asking the boss to try to source the part (the manufacturer was long out of business) I brought in a used oil filter o-ring from the GoldWing and it worked perfectly. It was still working perfectly a decade later when I retired. I know that is working in tension instead of sealing but it is a pretty good indicator of how long something like that can last.
I shop online a fair bit these days and I hardly ever buy on Amazon because I can usually find the exact same thing elsewhere for less and I can almost always find what I am looking for easier somewhere else (if they would fix their search function and police the keywords that sellers use it might be better but as it is it is a terrible experience).
As for buying oil (or any other liquid for that matter) online, you must know that a significant part of the price is the cost of shipping ("free" shipping just means that the price has been increased to cover the cost of shipping) so buying online is almost always second only to buying it at a bike shop.
Besides, I remember being taught that step #1 of an oil change is driving to the store for the supplies so that the engine is fully warmed up and the old oil will drain better. Yes, I know that isn't always possible in the real world (I often have to take a ride to warm the engine because I bought the oil weeks before I needed it) but if you buy the oil online it can never happen.