Gauge SEO Success

I was thinking the same. This timeline doesn't sound like something that a professional SEO agency would use.

Sure, stuff needs to be analyzed first, but it doesn't take the first month. After the first round of checks you should have at least an idea where the low-hanging fruits are, but even more thorough analysis takes a few hours at the maximum. The client isn't likely paying enough for everything to happen in the first month, and on-page SEO is something that needs to be fixed first, but I don't see why it'd take that long to start building links if that's a problem (and it often is). Content creation and link building should run in parallel.

If your SEO agency spends a month by "starting to focus" on content creation you know it's time to cancel the contract.

If your SEO agency wants to "start social media management" as a part of the SEO process it's time to have a serious discussion about the goals of the project.

Again, it's impossible to say if you're not willing to give any details or even a frame for this apparently hypothetical project were discussing here.

But I'd say that a year is enough. If it's possible and feasible with your resources you should be ranking for something. If not, you should've learned that lesson in much less time than a year.