I retired from 20 years in a civil service job at age 54, in 1998 after a huge runup in the stock market. We had always lived well below our income and saved the difference. When I saw how much our savings jumped up in the year-end statements 12/96 and 12/97 from Fidelity, it got me thinking that we might have already attained our goals.
I bought Quicken retirement planning software after talking to financial consultants who knew less than I did. (MBA in 1975). The Quicken software ran the same mathematical projections that a consultant would. My problem with the Fidelity 'advisor' was he wanted a percentage to run my portfolio - no thanks - and he would look only at the Fidelity numbers. I asked him for a consult on how I was doing in self-managed IRAs where my employer was the custodian and he wouldn't even look at the documents (showing balances comparable to the Fidelity statements) so I walked. Lesson: Find the right advisor! 'Free consult' is often a sales pitch. Fidelity has been excellent over the years, this was the only exception.
17 years later I can confirm we made the right decisions. First, to live comfortably below our total income. Second, retirement has matched the projections I made back then. It amazes me that our savings balance today is about 90% of what it was when I retired 17 years ago because we have generally been living within our pensions and savings earnings. Last year I started the age 70 'Minimum Required Distribution' from my IRA, and my wife will soon start drawing some $1,500/ month SS when she turns 70 plus her own MDR. These new income streams plus paying off our city house in a couple of years ($1,100 payment) frankly will boost our spendable to more than we have use for. I should buy a boat.
My point to anyone looking at retirement from the vantage of youth: Save all you can while maintaining a comfortable life. Get a consultant, or software, that illuminates the tremendous power of compounding over decades. Plan so that you can survive hard times comfortably if jobs etc disappear, if you are lucky that reserve will allow early retirement.
And note 85% of all investors don't exceed the simple strategy of buy and hold an S&P index fund, so consider that for the core of your savings. Ignore market fluctuations (although I think the market is heading down into 'buy' range at the moment).
Like several of you in this thread I started from nothing and my first career was fixing up rentals. The secret there is rentals sell at a multiple of the rental income. Transform a trashed rental in a decent neighborhood into simply average for the neighborhood, and resell it for a lot more than you paid. Three years of that allowed me to be a full time MBA student while continuing to manage the rentals. Projections I ran in my finance courses revealed selling the 9 units and carrying (all or part) of the buyer's mortgages paid me the same as operating them and no more management headaches. As those properties re-sold subsequently and cashed out my equity, those big chunks of cash were the foundation for starting substantial savings. I don't know of another occupation so easy to get into that pays as well. All it takes is patience to deal with the one tenant in 20 who would drive you crazy if you don't face the problems he/she causes. This isn't free income, you earn it.
As for bored in retirement - I can't imagine that. Every day there's more to do than hours in the day. 20 years crunching numbers (construction-cost auditor, pays well, some interesting travel to every corner of the state) was a mostly boring but essential detour out of a lifetime of doing what I wanted.