I think of being rich as thinking about the value of things rather than the cost. Super-rich is not thinking about the value or the cost but just buying what you want.
By that reckoning I am already rich as I can afford to buy flash cars, jewellery, designer clothes (although probably not all of them all the time) but choose not to because that's not my preferred lifestyle. Even for the super-rich there are probably things that they pause to consider before buying because it's so expensive, an extra Lear Jet or a house in the Hamptons for eg.
I don't think DH will ever chose to stop working as he's a workaholic, but I guess if he did stop we would probably continue our lifestyle indefinitely with a capital of about £4m.