A good month is a higher mileage than the previous month, especially in Feb when there are only 28 days.

It's all relative. Ride as much as you can without getting burnt out. I rode over 1,000 miles one month, and that was a lot of riding. Seems like all I ever did was ride, and I was always riding over 60 miles each time. That got me nice and burnt out for the start of the next month.