I don't think I've ever taken offense to anyone forgetting my name. No matter how long.

I also try to make an effort to use people's names around me if it's a newer group. That being said, I've went a long time without knowing some names and it's gonna be, "dude", "bro", "friend", "you" for a while until I hear someone else use their name.

I once dated a guy I didn't know the name of for an uncomfortable time. We met when drunk and I didn't really remember it, I'd put his number in my phone as 'nice nails guy', cause he had nice nails.

Turns out as we chatted he was pretty cool, we started going out and after like 3 or 4 weeks he decided to introduce his new girlfriend to his friends.

That's when I learned his name.