I tend to do about 150-200 miles a week on average. Of course, I'd do more but I'd be breaking with my training schedule and I don't need to do more.
Also, to the guy who asked what were Cats and etc. Cat. 5 is considered the beginning Category, but don't get me wrong, some of those guys in Cat. 5 are still pretty competitive so don't expect to win all the time, you won't. Some guys just have more talent than others but they don't win every race. If you want to have a comparative measure, take a social cycling club ride and push the average mph 3-5 mph up, and that's your Cat. 5 race which tends to average 20-23 mph for a road race and 25-29 mph for a criterium (short course circuit race, also has time limits of 15-60 minutes).
Cat. 4, more competitive and better cycling habits by the participants, considered Intermediate.
Cat. 3, Expert
Cat. 2, Semi-pro
Cat. 1, Professional level, low level, and if you're a Cat. 1 rider, you'd better get your ass moving and get a sponsor or a pro team to ride with!
Also, to promote up from each Category, you have to meet certain qualifications. IE, with Cat. 5 to Cat. 4, you usually have to have 10 mass-start races on your resume. But Cat. 4 to Cat. 3 and so on, you have to accumulate a number of points to move up each by placing in mass-start races and you can get globs of points by winning multiple day stage races (overall GC) which means you'll get promoted quicker if you win stage races.
Note: This is the standard for USCyclingFederation (USCF) racing so don't expect to find the same system in other countries.
Thomas Davis