If not yet near retirement, conventional wisdom says you only really need enough cash (or similarly liquid assets) to cover major emergency expenses that you couldn't cover using your current income from working. If you're retired, and you're drawing your living expenses from your nest egg, the conventional wisdom is you need enough stable, liquid assets to enable you to avoid having to tap more volatile, beaten-down investments during a recession. At least that's how I understand it. Obviously there are scenarios in between that one may want to consider, such as the likelihood of losing one's job in a recession. Maybe the less job security one has, or less reliable a stream of income from work, the more of those stable, liquid assets you might want to have on hand.