It's not uncommon if you're in charge of critical projects that you give your employer an extended window before you leave so that they have a real chance to hire someone to replace you and you can get them up to some kind of functional speed.
Would the company be concerned about you or your financial obligations if they decided to lay you off?
Yes out of courtesy I’ve helped former coworkers by answering questions. But I’ve slso made myself available on a contract basis to a former company.
And how many have taken you up on the offer? I'm 0/2. Usually people don't like people leaving them.
But that’s only because the company I was working for laid everyone off [1] when another company acquired us for scraps and our corporate customers. The customer I was working for made arrangements with the acquiring company to hire me as a contractor and gave me access to all of their (my) source code.
[1] the lay off was very well done. The company kept us informed of the situation the entire time we were struggling and the investors promised us that we would get paid as long as we were working. The acquiring company gave us each a month severance. We all had plenty of time to prepare and all of us had jobs lined up within two weeks.