Despite the name, I'm inclined to think regularity is actually more important than frequency.

A person who does 24 sectors in 2 weeks, then nothing for the remainder of the year, I would not describe as a 'frequent flier'. If someone did the exact same sectors, but as a consistent pattern of 2 sectors a month, every month, for a year I would say they were a frequent flier.

Comments above on "it's a scale" are also spot on. I average a flight every 3 days and pretty much everyone I know thinks that is a farcical level of flying. Compared to others on here however, that's pretty small beer.