You can access money from a 401k, roth, traditional IRA's before you turn 60- in multiple ways- and still get a great tax benefit out of it! If you are willing to do a bit of financial "hacking" you will have a lot more money, sooner, due to tax benefits.
Read this page, especially the "Roth IRA conversion ladder" section.
In short, after retirement you can convert money from a 401k etc to a roth IRA, pay lower taxes than you would now, and use that money 5 years later with no fees.
If you are willing to do that, the ideal savings hierarchy is: 401k up to your employer match, then max your traditional IRA. If you can do that, go back and max your 401k and THEN invest in completely taxable accounts. That should shave more than a few months off of your required work years.