The cool thing about this approach is how nicely it works with compound interest.
Live like a college kid for the 5 years after you leave college, and I defy you not to put $10k per year into the market. Fresh out of school with my $32k salary, I'd regularly find month-old paychecks lying around undeposited because I simply didn't need the money to support my cheap apartment, used car, and 10lb sack of potatoes.
With nowhere for your money to go but the market, you quickly discover what 10%/year (or even 5% per year) does to a stack of money. Eventually it's making more on its own than you're putting in. Financial security for life, sorted by age 30.
In 1998, a reasonable expectation was 50% per year, though you'd usually beat that if you invested in anything starting with a lower-case 'e'. Naturally, it all went away if you left it in, but that's beside the point.
Today, it's still not unrealistic to expect that money you put in today will make on average 5-10% per year over the next 40 years. If you're investing your money for a shorter period than that, it's not really retirement savings but speculation, which can be fun but is its own thing.
Regardless, I don't think I'd discourage people from saving in their 20s because you don't think the market is going to continue doing its thing. It'll be back, and the few hundred K that you can set aside in your 20s will do some amazing things over the course of your life if you invest it in index funds rather than granite countertops.
To really understand the situation start running the numbers of late life salary bumps.
It is difficult to balance lifestyle, income, and savings as you start to ramp up your salary AND your lifestyle. If your salary doubles between 20 and 30 and then again between 30 and 40 your savings does not change. So even if your saving 20% of your income every year you are not going to be able to safely retire at 80% of what you make at 40. Unless, you get a salary bump and don't increase your lifestyle.
Take it further; someone that sees a 3x gains from 30 is going to need to save ~40% a year to avoid a lifestyle drop. Meanwhile your friends are all raping up their spending and possible over extending.
This is my exact situation. I'm 24, finished engineering school 2 years ago, and work as a web developer. My lifestyle has stayed the same (I even spend less on many things). I don't need/own a car and don't really care about buying expensive gadgets...
I'm currently reading The Investor' Manifesto* and it seems I am very lucky to have money to invest in the market. A bear market is a boon for young investors.
Live like a college kid for the 5 years after you leave college, and I defy you not to put $10k per year into the market. Fresh out of school with my $32k salary, I'd regularly find month-old paychecks lying around undeposited because I simply didn't need the money to support my cheap apartment, used car, and 10lb sack of potatoes.
With nowhere for your money to go but the market, you quickly discover what 10%/year (or even 5% per year) does to a stack of money. Eventually it's making more on its own than you're putting in. Financial security for life, sorted by age 30.