I wasn’t complete in my original answer, so let me clarify: March 2017, I had an offer with the DoD. All paperwork submitted April 2017. This is for a secret. I hear nothing at all for 14 months.
In June 2018, I accept a new job that requires a TS/SCI. I let the old job know I am no longer interested, and ask them to close out the investigation which was still ongoing. TS/SCI paperwork all submitted in July 2018 (apologies for saying December - that was a mistype, I confused it with something else I was typing for work lol), March 2019 was background investigation, and nothing since then.
So with that first secret clearance and the current TS/SCI, I’ve had 2 investigations, no clearances granted, both at around 400+ days. I don’t think I have anything on my SF86 that would cause such a delay other than me living in 4 different states the past years.