As of late 2014, you can now (sometimes double) your retirement contributions and, best of all, roll the increase to your Roth IRA when you leave employment. Your employer's plan and your cash flow has to allow for this, but here is how it works: Your "regular" 401k contributions can be as much as $18,000 ($24,000 if you are over age 50). Your employer may or may not match part of that contribution. The total you are allowed to contribute is $53,000 ($59,000 if over age 50), so the difference between that limit and your prior employer & employee contributions can be contributed to your retirement account on an after-tax basis (no tax deduction). However, when you leave, you can roll that entire amount of after-tax contributions to your Roth IRA. This is vastly better than the current $5,500 limit on annual Roth contributions (none if your AGI is over about $132K single, $194K married filing joint).
Retirement and tax rules can be complicated, so please contact us if you would like to hear further about this opportunity.