I have terrible general flexibility, which both causes discomfort and affects my form when exercising (for example, I fall off balance any time I try and do a squat). This is something that I'd very much like to change, but in the past I've never been able to make a dent in it, so I'd like to try and be a bit more objective and scientific in my approach this time.
My question is, essentially - what is a reasonable schedule to gain flexibility for a given motion? I want to know this so that I can adjust my stretching to see what is and isn't working, and I want to give the stretching enough time to show noticeable improvements.
As a general guidance, I'm looking to know, essentially, whether my gains will be mostly front-loaded or should they be consistent throughout the improvement phase, and roughly (order of magnitude), how long should it take to go from poor flexibility (e.g. I'm about 20-25cm away from being able to touch my toes) to normal flexibility (e.g. touching my toes). One month? Three months? A year?
Edit: Doing a bit of reading, I think I should probably clarify that from what I can tell, I'd like to improve static-passive flexibility. It seems likely that I'll be able to consistently do static stretches, though I'm going to try my best to do PNF stretches.