I’m confused. You have worked for 30 years, so clearly your DH doesn’t have some huge income. What does it mean you don’t have to work? You can get by on his salary for living expenses, healthcare, retirement funds, and college? What about helping your kids get established or if they have trouble launching? What if your DH gets laid off which is common and crippling after 50?
Your kids are likely pretty grown and independent, so I would actually say pivot into a higher paying field and leave your niche. It sounds like you have a passion job, especially since it allows part time work but is still demanding. I would look for more lucrative roles, maybe something in a gov role or university.
Now if your DH had a big payday and none of these are worries, I’m 100% for retirement. I’m just unclear from your OP exactly what is young long term plan.