Something else I would add - if you're working in the ups-and-downs world of startups and technology, you may have meaty and lean years and during the good years find you want to save more fore retirement than 401ks, SEP IRAs and ROTH IRAs (if you're not priced out) allow.

One handy way to extend your tax-advantaged space: buy Series I and Series EE bonds from Treasury Direct. Both are tax-deferred until you cash them in. You can purchase up to 10K of each type per year. They are government-backed, highly-safe fixed-income instruments.

I bonds will pace inflation (like TIPS) for up to 30 years. EE bonds have low 'normal' yields but they automatically double after 20 years (so around 3.5%/year annualized, better than the rates on 20-year Treasuries). These rates are better than what you get on the open market.

And unlike normal bonds, they won't kick out payments that are taxable along the way - you can save the tax bill until you have a lean year then cash them back out (in the case of I bonds at least), or save them to the end of their lifespan (or until they double in the case of EE bonds).