If what you really want is to slide into your splits with little to no warmup then you really should focus more on the strength of your core muscles and legs. This is the "Secret of Stretching" that many people go into denial about. I gave up lifting weights a long time ago because my TaeKwonDo training was to rough, I would be sore for several days after a class (I went twice a week because i could not handle any more) and I kept getting injured be it my shoulder or pulled hamstrings. My progress soon after my progress grew very little year after year and I had believed that it was because that was as fast as I can go. It was not until recently that I realized that my school was very good at teaching technique but does not know the proper way to train athletic ability and in fact they have severly slowed my progress. Today I have to hold back in my classes just so I will not be sore for weight lifting and and endurance training.
This is very hard for a lot of people to hear. I try to hint it to other students in my class and its like telling them there is no santa claus. I look around and see students year after year keep stretching and never seem to make any significant progress. They feel that just showing up in class is enough because they get a grouling hour and half workout that keeps them sore for days is enough but they never seem to grasp the point that maybe they are to weak to advance or maybe they just don't care and just want the belt, I don't know.
Through the many years of training that I have been through, which is really not that much, I have also come to realize that some students just don't want that type of athletic ability or flexibility that would make a person a great martial artist because of the work it requires but just want to accomplish a little bit at a time just to know they have the will to take on anything that comes there way in life. Sometimes it is more about making a better person than making a better martial artist. If you are this type of person than all the power to you, there is nothing wrong with that. People need challenges prepare them for the even bigger challenges in life.
But if you really truly want to take your skills to that next level than you must make a total life change. To have that type of flexibility that requires no warmup will take alot of work to achieve but at least it will take little work to maintain. If you have not done so yet, read all of the articles in the stadion columns
http://www.stadion.com/column.html. I especially like #'s 18 and 19 because they offer a rude awakening. Start organizing your training days so you can train in your martial art, strength train, and endurance train in the same week and not conflict with each other. Stretching scientificly talks about this for a bit in the isometrics section and the stretching columns go into more detail.
Oddly enough, I treat my Tae Kwon Do class as a endurance workout instead of a technique workout because of all the drills that we do. If your classes are similar than I would advise you to do the same. It works great for me because I can let my body heal longer. I practice techniques on my own at home on the apropriate day. If you can't join a gym and have no weights at home, at least learn about some body weight exercises that you can start doing. Start running or at least get yourself a jump rope. You absolutely must start working on your core muscles with abdominal and lower back training. Start doing situps, crunches and back raises on the floor. The more research you do the better you will understand what excercises and techniques will work for you and what does not.
As of right now, I have taken time off from my martial arts school so I can build up my strength and endurance. I lift weights twice a week with exercises like shoulder presses and deadlifts, train my abs and at least once a week with crunches and situps, train on techniques at least once a week and work on endurance once a week by either running, jump rope or rollerblading. I hardly ever relax stretch now and I do dynamic stretches once a day. I do not know if this is the best approach but I am trying it out to see what happens because I really want to focus on being in better shape.
Try to at least understand that being able to perform a split is only good at desplaying things like your strength and determination. Being able to do a split alone does not make you a better martial artist (It sure does help). A split shows other people that you put the work into abtaining that level of flexibility and you had the will and determination to achieve it. This is where people screw up. They go straight to stretching to have that image but fail to realize that it takes much more than stretching to achieve it.
hope I didnt overwhelm you,
Any questions I'll be around,
jrlefty
"If you love life do not waste time because time is what life is made of"-Bruce Lee