(NSFW) If you became part of a couple with someone you've been in a FWB relationship with for a long time, how long did it take for you to get used to that?

This has recently happened to me and the transition period has been interesting. I’m not sure I ever want to get into a relationship this way ever again. I enjoy what we had too much and it can feel funny calling the guy my boyfriend, even though I really care about him a lot.

Key:
FWB = friends with benefits