I front-loaded my 401K contributions this year and as of today I am fully funded for 2017. This makes me exceedingly happy. I know others here do it too, but it's kind of an exciting jolt.
Now, for the remainder of the year I'm trying to decide whether I should take the same amount and do either megabackdoor Roth or just put it into my Vanguard index funds. I'm leaning toward the latter because I may make a job change around Q1 2018 or take a sabbatical and want the security of knowing the money is liquid.