Depends on how smartly you go about it.
You have to eat cleanly - abs are made in the kitchen basically. Here is what you need to know:
Nutrition (80% of the deal):
Get your carbs mainly from leafy vegetables and some fruit, get your protein from lean meat and egg whites etc, and make sure you eat enough (good) fat - like almonds.
Do not eat bad carbs like pasta, bread, cereal, rice or any type of grain food. This may come as a surprise but these kind of foods have a nutritional value close to zero and they make you store bodyfat. Simply put, humans aren't designed to eat these artificial foods so it's no wonder people are so obese nowadays.
I (highly) recommend "Mastering the Zone" by Barry Sears.
Exercise:
You can't spot-reduce, so forget about crunches etc for now. You have to reduce overall bodyfat to get definition, so concentrate on doing that.
High intensity, short duration, non-machine is what you should be thinking. An hour on the exercise bike maybe the norm, but you would be much better off doing simple interval training (go to your local football field and sprint around half the field and walk around the other half. Repeat ten times without rest. Scale according to ability. Do this twice a week at most). There is no-one about at 7:00a.m. so there's no excuse!
Twice a week of 20 minutes running may not sound very much, but it you do it properly (i.e. you're very out of breath at the end) then it will work at least ten times better than medium intensity work (no exaggeration). Interval training is just so simple, but wildly effective.
Edit: Okay, you do interval training. That's great. But how's your eating?
I still think that ab work is a waste of time. You are slowly strengthening them but it's not doing anything to remove the fat that surrounds them.