Is SEO a long term career?

And also, the domain you work in changes your task and most of the time, you learn new ways for SEO. There are different search engines and all the most popular search engines keep changing their algorithms to display results. So SEO is definitely not a bad idea in long term.

No, this is not true. SEO is a vast field and the techniques and strategies keep changing. You have to keep adapting to these and keep upgrading yourself. And also, the domain you work in changes your task and most of the time, you learn new ways for SEO.