Quoted:
I would at least consider something besides the target 2050 fund and what I would consider would be a straight S&P500 fund or a Total Market Index fund which I'm sure USAA has. Why? All target date funds do is assume you will be some age (doesn't really matter, let's say 60) in 2050, they derive your current age (25) and then use a formula which is something like 100-your age to determine the amount of your $ to put in stocks (75% in this example) and the rest (25%) in bonds of some sort.
The "problems" are, you may not be 25; you may not retire when you're 60; you can do the same thing for yourself with better and more cost effective funds; and the biggest one of all (especially based on your comments of having "extra" $ to invest) is that in the long run, your overall return is less since they will always invest some percentage in lower yielding bonds versus higher yielding stocks.
Assuming you are about 25, the "best" (highest overall return in the long run) is to go 100% (or almost) stock...like the S&P500 Index which I'm sure USAA has.
Not only is it
not dumb, it's an excellent idea to invest what you can outside of your Roth. The biggest question you have to ask yourself is how likely you are to need the funds you put into this "side" account. Just like the target funds shift more and more of your $ to bonds as your (theoretical) retirement date approaches, if you think you might need some of your "excess" funds within a few to 5 or so years, you may not want to invest it 100% in stocks unless you can withstand a potential drawdown (i.e. the stock market goes down but you need the $, forcing you to sell at a loss). Longer than 5 or so years and it's probably safe to go more heavily into stocks.
Bonds, BTW, are not an attractive investment (to me) right now since interest rates are near zero; they have only one direction to go (up) and when they do so you will lose principle (the money invested) in the bonds. People think bonds are safe but right now their real returns are negative, especially in a taxable account: you are assuming a significant interest rate risk for zero (or less) return.
When you say "I'd just trust that a pro knows what he's doing" it makes it sound like your alternatives are Target Retirement and rolling the dice, either by your hand or that of a "pro". The idea isn't to beat or play the market, the idea is to use a relatively simple set of sound
investment strategies to take what the market gives.
The simplest of those strategies: stick every penny that you can in the S&P500 and forget about it for a few decades. Assuming you are about 25 you will have millions by the time your 60 or 70. Someone will be along to recommend everything from penny stocks to gold as better investments than the S&P...and while the S&P may not be
the best vehicle, it is the single best investment if you don't know what you are doing.
If you have the time and inclination, check out asset allocation (a gross form of which is what the target fund does for you).
Finally, a
link with more links from a similar question.
ETA: left this post to check the market and...it's another good day in a good week!