RE: Is it really necessary to pin nylon or CA hinges?
Every chance you get, do an autopsy on any crashed model you can. And if you can, do some destructive testing of the hinging.
I've done that on every model of mine that bit the dirt to see how well I built 'em, since we built 'em with stone knives. Since ARFs took over, there isn't much of your building to test except the hinging. You will see if your technique is adequate or not. You will be amazed at how impossible it is to pull CA hinges done right. And you won't be able to tear 'em apart either.
As for the hard nylon hinges with metal hinge pins, if they have holes in the flats and you used enough glue, you'll not get them out or defeat 'em either. And that's with either epoxy or hinge glue.
But if anything makes you feel more secure about your models, especially pinning, then do it. We build for fun and pride, don't we?