I also have a years' worth of living expenses saved, and it also took me about 3 years to build. It has zero impact on my stress level at work. I don't think I feel any more free to leave than if I only had a months worth saved. The idea of leaving and potentially burning through most or all of that portion of my family's savings while I look for another job is no more appealing or satisfying than just staying in the stressful job.

Perhaps I'd feel differently if I had several more years saved or if I were more stressed at work. The thing about work stress that builds up is that your mental health declines and you can begin to think very irrationally. Paranoia and depression can set in. I've seen devastating examples of this with people I know. I think it's important not to minimize it or brush it off and to understand that what seems obvious to you or I may not be obvious at all to someone who is feeling burnt out, desperate and depressed from their work situation.