How much do O-rings last?

Hi guys, I was wondering how much o-rings last, since today I did my 2nd oil change (at 4000km), the first was at 1000km, and they changed the o-rings. Now after 3000km and ~1.5 months I changed oil (with Motul 7100, originally should me Yamalube Semi-Synthetic) and oil filter (with OEM one) since that's what the manual says. But I haven't changed any o-rings. Should I change them, or just leave them, and change them at 7000km? (6000km after the first replacement)