OP, historical processing times have varied widely. Our AOS in 2018/19 (straightforward also) took like 13 months with an interview. ROC took 18 months, no interview. There were people here on VJ with timelines similar to ours who had much shorter and much longer wait times. There is not always rhyme or reason, and the local field office greatly impacts it.
Like others are saying, start reading and following the threads here on VJ that align with your timeline. The more you read and research, the more likely you are to be successful with US immigration.