As someone who tried to make the exact same plan for the exact same reasons, I kind of have to chuckle at the responses.
So, I intended to keep working full tilt, pedal to the metal, until my early 40s so that I could secure my comfortable FI and be free to physically fall apart after that point if that's what I was destined for. I was in relatively pretty good shape when I started working at 31.
Well shit, that didn't really work out. By 34 I was already falling apart and dropped my workload dramatically, and by 37 I literally couldn't physically do it, or much of anything, anymore.
Now, that's not to say that that's your fate, you might hang in there just fine into your senior years, who knows. But serious, chronic, potentially disabling illnesses don't tend to be predictable. Mine escalated FAST, and it wasn't until it was too late that me and my medical team figured out that the job itself was directly worsening my condition.
I was basically uninsurable, but through my professional organization was able to maintain a very small "own occupation" LTD policy that didn't require underwriting, so that helps, but only because I'll be able to invest it and let it grow, not actually try to live on it.
So what do I recommend?
Well first: watch what your job is doing to your body. If you are being at all overloaded, you have no idea when your systems could go into total failure. There's a temptation to push hard now to reach your savings goal, but what happens if you don't make it?
Second: build resiliency into your plans. The moment I knew I was vulnerable, I dedicated myself to expanding my work options to include multiple part time income streams that I could do even if I was totally physically fucked. This is why, even in my mangled state, I have more high-paying, interesting work options than most able-bodied people do.
Third: absolutely try and get yourself an LTD policy, or see if there's any way to get back on to your employer's policy. If you manage to get a policy, find a good disability lawyer and invest in an hour of their time to understand how disability claims work. I wish I knew years ago what I know now about what I needed my doctor's to document in their notes. I could have dodged a long, difficult, and expensive process had j just been a little more proactive. Thankfully, I was proactive enough to contact a lawyer *before* I filed my initial claim, but I wish I had thought to do it when I first purchased it and knew I would probably use it someday.
Fourth: thoroughly research what kind of medical support you might need. What specific disabilities do you think could lead you to requiring ongoing nursing care? A lot of very disabled people manage to not need full institutional support if they're fully cognitively functional. So understand the varying levels of care you could need and what they might cost. Thoroughly research what programs exist, even though they can change over time, it helps you become familiar with navigating the system.
Overall, be very honest with yourself and your spouse about what the actual impacts of disability would be. How would it affect your shared life? How would you stay fulfilled and happy? What are the biggest real life risks to your collective well being, not just finances. The money is just part of the big picture.
For me, between managing to get debt free, keeping our expenses low, DH making enough money for us to live on, having a small disability policy, having multiple options for non-physically-damaging work, having a DH who is a certified nurse's aide who used to work in a nursing home, and a family full of people with complex medical issues who have been-there-done-that. For me, it isn't this big boogeyman that can ruin my life.
I mean yeah, it utterly fucked my career, but my life is still pretty awesome because I've spent so many years realistically preparing for this, and not as some kind of apocalyptic/worst case scenario kind of thing. Just as a normal part of being a person with certain health risks.