I’m a little older (ok a decade older) and have been running the numbers for my own plans… The big kicker in every retirement budget I come up with is health insurance.

My husband is older than me, and will qualify for medicare in 6ish years. I’ve got 16 years. Kids (2 of them) will need insurance through college.

My goal is to get my house paid off early. (If things go well in 5 years or less.) After that, the other big budget item is health insurance. For a family of four, using a lower cost insurance (Kaiser Permanente HMO) it’s still over $13k/year. That’s a big chunk of money on a limited budget retirement.

If you use Quicken – they have the “financial overview” feature that you can plan all of your expenses vs savings/investments… You can put in stuff like college for the kids, when social security kicks in, when you can start drawing your 401k/IRA funds without penalty. You can play with the rate of return, etc… The key is coming up with a reasonable budget in the first place… then adding overage because…well, $hit happens in real life.