How much will my expenses actually change once I retire?

A common rule of thumb is you'll need 70% to 80% of your pre-retirement income, but real spending rarely stays flat. Many retirees see a busy, higher-spending 'go-go' phase in their 60s full of travel and hobbies, a calmer 'slow-go' phase in their 70s as activity tapers, and a 'no-go' phase later when spending drops except for healthcare, which can spike. This pattern means your income plan shouldn't assume a single unchanging number for 30 years. Budget generously for the early active years, expect a natural decline in the middle, and reserve a cushion for late-life medical and long-term-care costs, which are the biggest wildcard.