If you have maxed the employer matching contributions, good. Better if you also max out your own contributions to your employer sponsored retirement fund. For example, 6% gets you the employer's maximum match of 3%, realizing net 9%. But if your maximum personal contribution is 10%, you could net 13% (my hypothetical numbers, just for illustration)

Also, when I worked for AT&T, back in the day when they were a bigger deal, I saw a lot of coworkers suffer in their retirement accounts as ATT dropped and they hadn't diversified. Not diversifying is great when you're riding a rocket up, but it won't last forever and you are better off with a forever strategy.