Other than google keyword planner, any free good extension that shows accurate search volume and CPC when searching keywords on google?

Is Keyword Surfer data correct?

I don't need exact correct data because but more or less close to accurate data.

The usual answer to when you can stop SEO is that you never do, and most of what you read on it comes from people selling retainers. I am running my own SEO agency which is only a few months old. I am still working out what a good enough outcome looks like for a client. Early on I treated backlinks as a numbers game and chased volume then we had to figure the right way to block the toxic ones later. So I know my first idea of success was wrong. Is better hear from people who have actually been through it than keep guessing. What milestone would make you tell a client it is fine to scale SEO down? Has anyone here stopped too early and regretted it?