EDIT: By "not touch it" I meant invest it in something safe and easy and then you'll have full retirement money in 30y
At any rate, it's not $600k, because OP is going to retire in 30 years. Reasonably invested, I think you could get that up to $2.5M or so by then. And presumably OP won't be spending every cent of income over the next 30 years and will continue contributing to that nest egg, even if modestly.
A 4% withdrawal rate is probably safe if the retirement horizon is only 25 years. On $2.5M that's $100k/yr, which is plenty for most places in the world. Yes, inflation complicates things somewhat, but I think OP will still be fine.
Well, they are 35 years old and have $600k, which says something.
You need an investment that at least matches inflation, and is large enough to cover fixed living + increasing medical costs.