I'll be leaving shy of 5 months in this role. I would have left before if the interviews had gone at a faster pace.
My manager is very aware that I've never been super happy, but I also have honest advice about what they should do about my role.
I actually think the company has been fair with me for keeping me for so long even though my role is entirely redundant. I'm planning to give them more than the required one week's notice.