Seeing your abs, or any other muscle group, for that matter - is almost entirely the result of having low body fat levels. You get low body fat from proper diet (as well as cardio and strength training), not from doing hundreds of ab exercises every day.

You didn't mention whether you knew your body fat level or not. My guess is that it may seem like your lower ab muscles are "hard to develop," but it's not really an issue of "muscle development" at all, you simply have too much body fat and are storing it in your lower abdominal region more readily than other parts of your body and you can't see the muscles through the fat.

Most people don't have their fat distributed evenly throughout their bodies. Each of us inherits a genetically determined and hormonally-influenced pattern of fat storage just as we inherit our eye or hair color. In other words, the fat seems to "stick" to certain areas more than others.

Men often tend to store fat more readily in the lower abdominal region (the "pot belly", "spare tire", "beer gut", or "love handles"). In women, the "stubborn" areas are usually the hips, thighs ("saddlebags") and the triceps ("grandmother arms").

You could focus on more "lower ab" exercises like hanging leg raises, reverse crunches and hip lifts ("toes to sky"), but even these won't help as long as you still have body fat covering the muscles. You can't "spot reduce" with abdominal exercise.

The lower abs is often the first place the fat goes when you gain it, and the last place it comes off when you're losing it. Think of ab fat like the deep end of the swimming pool. No matter how much you protest, there is no way you can drain the deep end before the shallow end.

I would suggest cutting back the volume on your ab training and spending that time on more cardio work instead. Personally, I only do about 15 minutes of ab work two times per week. (About two to four exercises with reps usually ranging from 10-25 reps).

Here is a recent ab routine that I used (for bodybuilding/ ab-development purposes). I do this routine only twice a week and I change the exercises approximately every month so my body doesn't adapt. I prefer slightly higher rep range than other muscle groups, but as you can see, it is far from doing a thousand reps a day. (if you want to see what my abs look like, just checkout my picture below

A1 Hanging leg raises 3 sets, 15-20 reps

Superset to:

A2 Hanging knee ups (bent-knee leg raises) 3 sets, 15-20 reps (no rest between supersetted exercises A1 & A2, 60sec between supersets)

B1 Incline Revere Crunches 3 sets, 15-20 reps

Superset to:

B2 Elbow to knee twisting crunches 3 sets, 15-20 reps

For maximum fat loss, you should do cardio 4-7 days per week for 30-60 minutes (the amount is variable depending on your results). You could continue running or mix up the type of cardio you do (stationary cycling, stairclimbing, elliptical machines, and other continuous aerobic activities are all excellent fat burners without the high impact and joint stress of frequent running).

If time efficiency is an issue for you, you could perform high intensity interval cardio training and achieve very efficient results with even briefer workouts (20-30 min per sessions, or less, if the intensity is high enough)

Once you are satisfied with your level of body fat and your abdominal definition, you can cut back to 3 days per week for 20-30 minutes for maintenance.

As far as nutrition goes, here are a few fat-burning nutrition guidelines in a nutshell:

Eat about 15-20% below your calorie maintenance level. If you use a more aggressive calorie deficit of 25-30%, then do not keep calories too low for too long; increase calories to maintenance or maintenance +10-15% 1-2 days per week.
Spread your calories into 5-6 smaller meals instead of 2-3 big ones. Be very conscious of portion size. eat too much of anything and you can say goodbye to your abs. Period.
Eat a source of complete, high quality lean protein with each meal (egg whites, lean meat, fish, protein powder, etc)
Choose natural, complex carbs such as vegetables, oatmeal, yams, potatoes, beans, brown rice and whole grains. Start with aprox. 50% of your calories from natural carbs and reduce carbs slightly (esp. late in the day) if you are not losing fat.
Avoid refined, simple carbs that contain white flour or white sugar
Keep total fats low and saturated fats low. Aim for 20% of your total calories from fat (and no more than 30%). A little bit of "good fat" like flax oil, fish fat, nuts & seeds, etc is better than a no fat diet.
Drink plenty of water - a gallon is a good ballpark to shoot for if you are physically active.

1000+ reps of ab work four days a week is an amazing feat of endurance, but thats not how you get visble, rock hard, 6-pack abs!

You probably have outstanding development in your abdominal muscles. (you certainly have great muscular endurance). Unfortunately, if your abs are covered up with a layer of fat, you wont be able to see them even if you do 10,000 reps a day!

You "get abs" from reducing your body fat and you reduce body fat mostly through diet and cardio.

if you want to learn more about how to BURN THE FAT off your abs so you can finally SEE them, grab a copy of my ebook BURN THE FAT, FEED THE MUSCLE, It's the "bible" of fat burning nutrition:

Tom Venuto is a lifetime natural bodybuilder, an NSCA-certified personal trainer, certified strength & conditioning specialist (CSCS), and author of the #1 best selling diet e-book, Burn The Fat, Feed The Muscle. Tom has written hundreds of articles and has been featured in IRONMAN, Australian IRONMAN, Natural Bodybuilding, Muscular Development, Exercise for Men and Men’s Exercise as well as on hundreds of websites worldwide. Tom is also the founder and CEO of the Internet's premiere fat loss support community, the: Burn The Fat Inner Circle. To subscribe to Tom's free monthly newsletter, visit www.TomVenuto.com/free_newsletter.