No kidding. When faced with a heatsink that doesn't have thermal paste (or for watercooling), I like arctic MX-4. It cools just as well, is a nicer consistency, and doesn't have to cure.
That being said, the difference between expensive goop like that or AS5, and the stuff that comes with a Hyper 212 EVO, is going to be a couple degrees at the very worst.
Yeah I was using the MX-2, I still have like half left. But that was when I had AMD CPU. Then after I did some research on how hot IVY BRIDGE is, I figured it was time to get a different effective paste and saw online recommended AS5 but they didnt tell me how long it takes to cure!
No worries, it's just something to know for the future.
Unless you're going for an extremely high overclock on water, you're usually just fine with the thermal paste that comes with the heatsink / whatever you've got lying around. (Just avoid the white thermal glue-type stuff.)