I think it really depends on how often you breastfeed/how long your child goes between feeds day/night.
For me, my child didn't STTN till last weekend. He breastfed or I pumped every 3 hours during the day and at least once a night. I started weaning from the pump during the day at work when he hit 12 months and I got my period back on his 13 month birthday. I have friends with children that slept for long periods at night early on, and their periods returned sooner. Same with friends who used the bottle more than I did.