After 4 years, it seems a bit strange. Unless she really likes cum somewhere else. I've let plenty of complete strangers cum inside me. Can't imagine a long term boyfriend not doing it.
I had impromptu anal sex at a party and hadn't prepped for it. After fucking my ass for a few minutes, the guy pulled out and I shit all over the bed. Luckily I didn't know him before that night and never ran into him again. Super awkward.
My biggest gangbang was with 12 guys. I've done it a few times at an adult theater. It's so sexy walking out afterwards with cum all over my face and dripping out of my holes.