How Long do you keep trying for a sibling?

My little angel is 19 months old, after two miscarriages this year and after a year of trying how long do we torture ourselves with OPKs, charting, tww and endless pregnancy tests before we just give up and accept that we may only have one child? Don't get me wrong, I am beyond grateful for my beautiful girl there are so many out there that would give anything for one baby but I grew up in a large family and would so love to see the bond of sibling love..