To be brutally honest, and I will probably be flamed for this, but I really wouldn't worry about it too much. If you guys plan to be married upon retirement, I assume the 401k is likely to be treated as "family" money. However, even if you split, Texas is a community property state, so.... It's likely his 401k will be divided evenly between you both (all that has been acquired since marriage, anyhow) if you do split, you won't be left penniless.
As far as planning for retirement, do you or your DH plan on retiring early? Here's why I ask - My DH and I have a similar age difference (8 years), and we plan on retiring early. I WOH (and am another TX NMY, wow we seem to be similar!
), and we both have 401ks - but we do put substantially more in his 401k than mine. If the money is in a 401k for him, it can be accessed penalty-free when he is 59 1/2, meaning when I am 51 1/2 (If we had most of our retirement money in my 401k - which is possible since I earn more than DH - we couldn't access the bulk of it penalty-free until I am 59 1/2 - no thanks, I'll retire 8 yrs earlier and put more in DH's 401k now, thanks!) The rest of the capital and earnings in my own 401k can grow until I am 59 1/2, or when my DH is 67 1/2 - and hopefully we will never have to access mine and can live off of "his". Basically, we're not too concerned about how much is in whose name, because if we stay married until we retire (which we plan to!!
), we will be in an awesome situation with lots of choices. And if we ever divorce for some reason, my own financial situation won't be compromised since TX is a community property state and both of our 401ks will be treated and split equally (we don't have a pre-nup).
Long winded answer, but I really think it's necessary to consider one's whole financial picture along with life goals and situations. It's awesome to even be having these thoughts, though! I know when DH and I started talking about these things, we absolutely were thrilled to have the privilege of talking about the future instead of just worrying about getting out from under our debt. Good luck with whatever you end up doing!