How long is my form taking?
USCIS publishes a range per form and per office. Both matter — the same form can differ by months depending on where it is being handled.
Forms decided centrally, at the National Benefits Center or Service Center Operations. Here the category of work is what changes the answer, not the office.
I-129F — Petition for Alien Fiance(e)
12.5 to 16 months
Service Center Operations (SCOPS)
Estimated median
11.3 months
The published range is the slow tail, not the middle: USCIS's low figure is where about 80% of cases have finished and the high figure about 93%. So half of cases finish sooner than 11.3 months — three in four by 12.3, nine in ten by 15.7. An estimate from those two published anchors, not a figure USCIS publishes.
Ranges are as published by USCIS: the low figure is where about 80% of cases have finished and the high figure about 93%. Confirm on Check on USCIS's processing times page.