I find this thread interesting and encouraging. I've been retired for 15 years and my contribution can be best summed up by a paraphrase of something that General Eisenhower said. He said that in battle, all your plans are thrown out the window but failure to plan ensures defeat.
My experience is that things change constantly. When I started my career, we didn't have IRAs, 401Ks, Roths, etc. We didn't have Medicare and only rudimentary Medicade (which I wouldn't qualify for if I planned properly). We had fewer pension rules and company benefits varied widely. Accordingly, salaries were significantly impacted by a company's benefit package and perceived viability. Throughout my career, these changes impacted my salary, health benefits, company-provided insurance, and, of course taxes (even in retirement) I'm not complaining; I'm only noting that, almost assuredly, there will be significant changes throughout your life. Technology and economies will change and invariably changes will be made to your earning power, income and retirement tax laws, and investment options. These changes will cut both ways and it would be extremely rare to expect that your circumstances would be dead-on average (e.g. the average family has 1.5 kids but yours won't).
Summarizing my advice:
1. Plan conservatively but plan. Underestimate projected investment returns or salary increases. Overestimate costs and taxes.
2. Review your plan when there are impending changes that impact the structure of your plan. I'm not saying that you should watch your investments daily and react to every movement; you can do that if that's your hobby but, as has been by someone else, there is no evidence that anyone can do that perfectly.
3. Review your plan on a scheduled basis; more frequently when you are younger and changes will be magnified.
3. Know that things will change. I wanted to be able to do extensive traveling when I retired. I am able to do that financially but our health and safety have changed so it's time for me to review my plan again.