If you're talking a straight up senior individual contributor without mentorship, leadership or ownership responsibilities attached, then I agree with what others have said about autonomy. A senior is given a problem or task and comes back some time later with the completed solution. If there is feedback, a senior will get clarification, go away again, and come back with an updated solution.
In my experience, this has required:
Technical competence and confidence (research, coding skills, digging into source code if documentation is sparse, having a good understanding of the big picture as well as the implementation details)
And equally as important (in bigger orgs), being able to seek out help/answers for org specific things that aren't googleable without hand holding. (example: getting a name of a potential subject matter expert from a tech lead and take it from there -- initiate the conversation, vet out the content, get a solid understanding -- without hand holding from the tech lead)
To more directly answer your question: Time isn't necessarily a factor. Demonstrating that the way you approach problems/tasks and the actual results you produce can be trusted and relied on firmly plants you senior territory imo.
Side note: as a 20 year vet, can you comment on my theory that I'm going to age out of software engineering? How did you make it 20 years? (Real question)
Honestly, that's kinda how it happened for me. When I remembered I liked coding I started tinkering with Python for a couple of weeks. I enjoyed it enough that I started to wonder if I could do it as a job instead of Electrical engineering. That's what lead me to look at education options.
If you're looking into web dev specifically... you could try writing some very basic websites for a week or two with HTML, CSS and maybe some Javascript. If you find your curiosity and your excitement when you get something to work outweighs the frustration of hitting learning roadblocks...then it's probably safe to say you'll like it and will thrive!
If you completely lose momentum and have no desire to try again or keep learning....then switching to it as a career will probably be a painful grind.
And to be perfectly honest, I didn't even really know what web development was when I joined the boot camp....I just knew I liked tinkering with the Python stuff that I did.
Bootcamps are definitely a gamble. They vary in quality too. But, I guess I'm just here to say that it worked in my case! So it's a valid option if the other factors make sense.
What is your current career? I was an Electrical Engineer until 2017 and was also considering a CS degree. I opted for a Web Dev boot camp instead as a lower timeframe/cost test of my ability to pivot.
I was able to land a job 8ish months after graduating and am now a Sr. Software Engineer. I think my previous engineering experience did help me get my foot in the door but one of my bootcamp grad buddies also broke into a web dev job without any bachelor's degree.
The CS guys here may scoff at me but the boot camp route made sense for me and it may for you as well.
It's definitely not a shoo-in. You have to like to code and have a passion for it. I liked it in high-school so it wasn't liked I just pulled the "lets try a coding career" out of thin air.
If you're talking a straight up senior individual contributor without mentorship, leadership or ownership responsibilities attached, then I agree with what others have said about autonomy. A senior is given a problem or task and comes back some time later with the completed solution. If there is feedback, a senior will get clarification, go away again, and come back with an updated solution.
In my experience, this has required:
To more directly answer your question: Time isn't necessarily a factor. Demonstrating that the way you approach problems/tasks and the actual results you produce can be trusted and relied on firmly plants you senior territory imo.