25 yrs ago, I did something similar.

I worked for a systems integrator that developed a turnkey software system for a client. It was a massive project (a systems migration) and ran for 3 years until handover. I was the lead on the project.

A couple of years later, I left my employer and joined a startup. 10-11 months later, the startup was looking to cut its burn rate and the CEO asked me to look for a job outside as revenues were not coming in as planned. He did promise me one thing. I could come back and join them after they became cash positive. He expected this to happen in 12-18 months. I trusted the CEO.

By pure coincidence, the client I worked several years ago was completely exiting operations from one of their operating locations (employees were offered to move to another city or leave with severance pay). The entire team that we had handed over the new turnkey system was being let go and none of the opted to move to a different city.

I applied for the job and got it. I told the management (they were from the other city) that I will de-risk the transition for them completely since I knew the system like the back of my hand and laid out one condition. I will stay for 2 years and will need a replacement to join in the 2nd year (there were some intricacies in the system that had daily, weekly, monthly and yearly processes) and I wanted my replacement to be trained on all steps. So, a year of overlap was justified. The hiring manager and the division VP, both interviewed me and agreed to this.

I did my job true to my conscience. As planned, I let them know at the end of the first year that a replacement needs to be brought in. A lateral hire came in as my replacement and I trained him and completed the knowledge transfer.

I quit after the second year as originally planned. My startup CEO rehired me back into their company which was now revenue-generating and cash positive. I joined in a senior leadership position.

That was one of the most intricate knowledge transfer of my career and I have been very happy. It wouldn't have been possible without the various parties trusting each other.

She was quitting because she was going to be a stay at home mother.

We hired the replacement and they worked side by side for ~ 10 months. It was amazing.

> Who will hire you with one year long advance?

They probably hired them ahead of time and had both working for a time. It can also take a long time to find someone.

Someone on my team just gave a 1-year notice a couple months ago. She hasn't lined up the next gig, and won't start seriously looking until later this year. She has more than enough cushion to cover a gap, and she feels some loyalty to the team to make it a seamless transition (she's been here quite a long time).

I could see this happening in a project based environment or with someone who has a long term plan to pivot away from work(travel/family/having kids/etc). If you're working on something pretty big, you might be willing to see it through, and quit before moving on to the next thing.

I wouldn't assume they were planning on a new job immediately. Could be maternity/paternity leave, a plan to sail around the world, whatever.

Could also be an in demand skillset. If you get interest every week, you're probably not worried about being able to find work in 10 months or whatever.

The part where the employee has self-selected themselves as a risk. Lots of the major companies have capability to identify when an employee is downloading tons of data and files, but for the less sophisticated ones, you pretty much just have to look out for motive, and an employee giving notice is probably disgruntled...which is at least a little bit of motive.