Well if you don't mind me asking, what kind of annual returns are you generating? If you're in the 7-8% range you're probably about as "optimized" as you can be, assuming your 401(k) is only giving access to large index funds.

Another trick you can use is switch to a Roth 401(k). It means you'll be taxed on your savings today, but when you retire they'll be tax free. Now this is total speculation here, but I'm kind of assuming taxes will be pretty high in the coming decades as we try to keep social security going and pay down deficit spending, not too mention dealing with climate change fallout.

Also good for you on keeping all your money in the 401(k) accounts, some people cash them out when they change jobs which triggers penalities and taxes. If you can however, I would roll all your accounts in to one giant 401(k) so you can better keep track of what's going on.