My problem is I don't know how much cash we will need coming in. I don't need to be rich but I darn sure don't want to be poor. Just comfortable. Food. Gas. Utilities. Taxes. My husband is older and I'm trying to get him to retire first. We can go from there.
That is a complicated topic. I have always approached it with the "having as much cash as possible" approach -- better "too much" than too little -- but at some point you have to stand up from the table. And "poor" is extremely relative, both to locale and experience.
If you carefully track your monthly expenses for a year, it will give you a very good baseline for how much you need, but you'll have to account for inflation, age-related increases in expenditures, and non-recurring type expenses (as often occurs around things like cars). You also have to know what you are going to do with all that extra time. One of the great ironies I've noticed in my life is that when I am busy working my butt off making money, I hardly spend any because I do not have the time. When I have time on my hands, I am far more likely to find creative ways to spend money that are not particularly constructive. I have also noticed that this is not unique to me. :-)