Originally Posted by
Tourist
Can we get back to fuel now?
No.
And back to the O.P., there are various rules of thumb for TLAR (That Looks About Right) altitude selection, depending on type. Many aircraft have charts for it as well, such as the A330 chart I'm looking at right now.
The old rule was "track mile distance divided by 10 equals cruise level in thousands of feet" plus a factor (add 5000 feet or something similar) for a particular airplane type. It works pretty well out to a couple hundred miles for a lot of types.