I like the simplicity of the 4% rule, even if I end up following the 3.5% rule or something else because your spending stays relatively stable. I believe I'll be happier if I don't increase my expenditures in good years only to decrease them in bad years. If I never get used to drinking the good whisky, I'll never feel deprived drinking the cheaper whisky.
With variable withdrawal strategies, you have to make sure that your "fixed" expenses are covered - barebones groceries, property taxes, utility payments - anything you consider essential. If your strategy doesn't cover these all the time, it won't work. Above this minimum spend, you have some "float". Now your float can be used for extras, but only things that can go away in bad times. It's this here today, gone tomorrow effect that turns me off to these strategies. Good things to do with float might include spendy vacations, charitable donations, house renovations. Bad things to do with float include anything with ongoing payments or carrying costs, unless they're neutral to your barebones spending.
Will my spending vary year to year? Absolutely. 8% of my budget is earmarked to sinking funds for replacement of longer-lived items, mostly cars. The money is there for budgeting purposes, but we'll leave the money invested until we need it. Then, every 5 to 10 years, we'll have a large expenditure year.
I expect if your plan is good and comfortable in your early years, it'll result in a need to blow lots of dough in your twilight years. When you first retire, your years left of expected lifetime don't change drastically from year to year, so your withdrawal won't be increasing as much as it will when you're older. A 40 year old male loses only 2.3% of his life expectancy when he turns 41, but an 80 year old male loses 6.2% of his life expectancy when he turns 81.
