I use AI to do software development. It has been super-helpful in learning about new technologies, what's available from big service providers like Microsoft/Amazon, how to get things configured, assistance with troubleshooting. Basically, everything that I would normally have to scour the web to figure out, it points me in the right direction much faster. It also hallucinates, so I still have to ask it for links and review them myself, but even with that, learning these things has been faster.
Not 5x faster. More like 2x on a good day, and only for learning.
For coding, I would say I have hit the 5x level maybe once or twice a year, for very specific tasks that involve writing some shiny new code that involves only common problems. For most of my work, maintaining proprietary systems that have a lot of legacy code from over a decade ago, the code generation just doesn't help. I have tried those tools that integrate with your IDE and suggest code as you type, and they don't speed me up at all. Most of the time they literally get in the way and break my flow of thought. I turned all that off. I have also used Cursor and told it to make changes for me, and it helps a bit with simple requests (but nowhere near 5x nor even 2x overall), and with anything complicated it just screws too much up and I have to undo it all and do it manually anyway.
So, I think that the notion of sustaining that 5x increase is a complete pipe dream. The tech is nowhere near capable of doing that, even when fully embraced. And as others have mentioned, we are just talking about coding. "Software Development" involves quite a lot of meetings with clients (internal and external) and business process analysis and QA and troubleshooting and and what-not, and all AI can do is clean up your notes into a more formal document format. It's nice, but nowhere near 5x.