That's a pretty nice build, and should hold you for some time. You should be able to achieve a mild to moderate overclock with your setup. And no, if done correctly you wont significantly lowering the life of your parts. I recommend reading the overclocking guide if you haven't already, or do some general reading on how to overclock your system.
You will easily be able to handle those games you mentioned. I don't have SC2 so I can't tell you about that, however 40fps shouldn't feel choppy. Are your temperatures good? You can try enabling v sync as well, that might help.
The overclocking guide is at the top of the overclocking section