“Stretching seems like a pretty simple topic, however, there is a little more to it than most think.” ~http://jiujitsumag.com/all-about-stretching/
I’m always looking for stuff about flexibility. I’m not the most consistent stretcher, but I’m not the guy who shows up at Jiu Jitsu class and jumps right in to rolls without doing anything. I have to warm up at least a bit (partly because I’m old as fuck and partly because my knees don’t work), if for nothing else then to get the blood flowing. Every now and then I make a great effort to improve my flexibility. Truth be told I would love to be a master of rubber guard. But after a while when I see no signs of improvement, I slack off a bit.
Anyways, here’s a good article from Jiu-Jitsu Magazine on different kinds of stretching and range of movement.
http://jiujitsumag.com/all-about-stretching/
The end
Mountains to Mats 
I have found that flexibility is an expression of the strength of ligaments/tendons. Super important for injury prevention.