How long have you been working on flexability? I'd just stick at it mate and give it a chance. I know I have deffinetly improved flexability. Deffinetly agree that you might have a head start the younger you start doing it but it is still atainable... I'm not sure if doing the splits is a bridge too far, but I'm more inclined to think that it isn't -- we shall see I guess.
I know workouts are less enjoyable, more grueling and overall physical well being is very noticeably reduced when I neglect stretching and flexibility. If I had to choose between strength training and flexibility type training, then I know I'd opt for the later as I have walked around like a crumpled up Lilt can in the recycling bin a few times, and it isn't nice.
It's like I've heard said a couple of times. People think sports stars like premiership footy players are the pinnacle of fitness and health, but how can they be when they retire at around 35 years old with list of injuries and ailments? Then look at Ryan Giggs who shows no sign of slowing down -- he's been practicing yoga for the last 5 years or so. You can see his physic has changed over the last few years as well. He has never been stocky but you can see he more svelt than he used to be.
There's a book on Amazon called The Shaolin Workout you might want to check out. Also, there look for something called The Stretch Deck; this is just a deck of cards (50 I think) teaching various stretches for every part of the body, and there's a 'game' on the DS called Lets Yoga which is also very good, contains loads of posses and tips and you can pause and spin the 3d model around to see the pose from any angel, very detailed peice of software believe it or not.
I would say it took me about 6 months when I first noticed the benefits of flexability training, doing it more or less every day...