Let me focus on the retirement number. I wrote a blog post on just that, The Number. In which I offer an easily editable spreadsheet to help users see if they are on track. With a goal of having 20X one's final income(1) at a retirement age of 62, at age 40, you should have just over 5X your annual income saved. If your income is $70K or less, you are doing great, much over $100K, and you are falling behind.
If your question is about your investment mix, yes, it's good not to have all one's money in pre-tax accounts when retirement comes. I retired at 50 and will tell you first hand, it's a strange thing to look at a retirement account balance, and feel the pressure to avoid withdrawals that will be taxed at the next marginal rate, or phase out some tax benefit. I'd strongly recommend you consider a Roth 401(k) if available. If not, try to fund the Roth IRA every year. It with give you more flexibility at retirement.
More on Roth - The pretax accounts are great. While working, you get to take money 'of the top' i.e. at your current marginal bracket, but at withdrawal, you start at zero, literally, for a couple, the first $24K of income is not taxed at all, zero. That said, there is a point of diminishing return, as your withdrawals go up, your top bracket may be the same as when working or due to phantom tax brackets(2) even higher. If one can make use of the Roth during the saving phase, you get to decide when to withdraw from the account at retirement. The IRA/401(k) are subject to RMDs, by age 78, forced withdrawals are 5% of account value. This can have the nasty effect of pushing you bracket far higher than planned. Consider, you might be taking withdrawals to be at the top of the 12% bracket, but the next $1000 will be taxed at 22%. And you need a new roof. You might have more than enough money in your retirement account, but this means the $10K 'costs' you $1K more in tax than it might otherwise. Just an example.
(1) 20X final income. This is a 'rule' of thumb. It combines a 4%/yr safe withdrawal rate, and a desire to target about 80% of one's final years income as a retirement level of withdrawals. Why 80%? No FICA, and no 'saving'. If you save more, you are living on less, and that replacement ratio can be brought down. Using 20% towards the mortgage? Once paid off, you might consider 5% for home repairs, etc. It's a moving target.
(2) Phantom brackets are what happens when the next bit of income doesn't just experience your normal marginal rate, but also triggers a phase-in of another tax such as social security (at $32K, joint) or phases out a deduction such as Schedule E real estate losses (at $100K, joint). The effect, for example, is that the next $1000, potentially taxed at 22%, actually cost you nearly $400 in tax.