I'm still getting 30mpg as an average for the year and a half i've had mine. Mostly 75 mile a day commutes (with some spirited driving, not all miss daisy) so no town driving which would kill that.

If you drive it hard then you'll not see 20mpg; drive it respectfully and you'll get 30+

If you're doing 300 miles a month then I wouldnt worry about the MPG at all and just enjoy it as it is great fun