Unless you have reason to think your opponents at this particular table will both notice and adapt to your bet sizing, you can open for more with your premium pair. 5-6x is fine. Even 8-10x isn't out of the question.

Note that the idea isn't to get them to fold. It's that people at this level will often do the same thing whether you 3x or 5+x. This being so, you want to get them to put more in the pot rather than less.